WO2020131040A1

WO2020131040A1 - Pulse width modulation driven heating sources

Info

Publication number: WO2020131040A1
Application number: PCT/US2018/066311
Authority: WO
Inventors: Daniel James MAGNUSSON; Robert Yraceburu; Vladislav SHAPOVAL
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2018-12-18
Filing date: 2018-12-18
Publication date: 2020-06-25

Abstract

In some examples, a device for pulse width modulation value calculations can include a non-transitory machine readable medium storing instructions executable by a processing resource to portion a control cycle based on calculated pulse width modulation (PWM) values of a number of heating sources driven by PWM signals, wherein a first portion of the control cycle is associated with a first heating source and a second portion of the control cycle is associated with a second heating source, receive a feedback signal from a sensor associated with the second heating source while the first heating source is driven by a PWM signal during the first portion of the control cycle, alter the PWM value for the second portion of the control cycle associated with the second heating source based on the received feedback signal, and apply the altered PWM value for the second portion of the control cycle associated with the second heating source.

Description

PULSE WIDTH MODULATION DRIVEN HEATING SOURCES

Background

[0001] Imaging devices, such as printers and scanners, may be used for transferring print data on to a medium, such as paper. The print data may include, for example, a picture or text or a combination thereof and may be received from a computing device. The imaging device may generate an image by processing pixels each representing an assigned tone to create a halftone image.

Brief Description of the Drawings

[0002] Figure 1 illustrates a medium storing instructions for pulse width modulation driven heating sources according to an example

[0003] Figure 2 is a block diagram of a controller including processing circuitry suitable for pulse width modulation driven heating sources according to an example.

[0004] Figure 3 is a block diagram of an imaging device including instructions for pulse width modulation driven heating sources according to an example.

[0005] Figure 4 is a diagram of a control cycle associated with pulse width modulation driven heating sources according to an example.

Detailed Description

[0006] in some examples, an imaging system can include an inkjet printing device in some examples, the inkjet printing device can deposit quantities of a print substance on a physical medium in some examples, the print substance can create a curl, and/or cockle in the physical medium when the print substance deposited on the physical medium is not completely dry. In some examples, a number of physical properties of the physical medium can be changed when the print substance is deposited by the imaging system. For example, the stiffness of the physical medium can be changed when the print substance includes fluid droplets. In some examples, the physical medium with deposited print substance that is not completely dry can be referred to as partially dried media.

[0007] The curl, cockle, and/or other physical properties that change due to the print substance can make finishing processes difficult. As used herein, a finishing process can include a process performed by the imaging system or finisher device after the print substance is deposited on the physical medium. The partially dried media can provide difficulties when stacking, aligning, and/or finishing. For example, the partially dried media can have distorted properties such as a curl, a cockle, a reduction in stiffness, increased surface roughness, extruding fibers from the surface, misaligned fibers, and/or increased sheet to sheet friction of the media. In some examples, these distorted properties can be caused by printing fluid deposited on the physical medium and the physical medium absorbing the printing fluid. For example, the print substance can be in a liquid state that can be absorbed by a physical medium such as paper. In this example, the liquid state of the print substance can cause the distorted properties of the partially dried media in a similar way that other liquids may distort the properties of the physical medium.

[0008] In some examples, a drying zone of an imaging device can be utilized to fully or partially remove the liquid and/or distorted properties from the partially dried Inkjet media. The drying zone can Include, but is not limited to, a number of air flow devices, pressure rollers, heated rollers, and/or heated pressure rollers in some examples, a heated pressure roller of the drying zone can be utilized to remove or reduce the distorted properties from the physical medium or partially dried medium. For example, the heated pressure roller can be utilized to apply pressure to a surface of the partially dried media and apply heat to the surface of the partially dried media in this example, the applied heat and pressure can remove or substantially remove the distorted properties of the partially dried media.

[0009] In some examples, the drying zone or a component of the drying zone can include a number of heat sources (e.g , heat generating device, halogen lamp, resistive heating wire, ceramic heating source etc.) that can be utilized to increase a temperature of the drying zone and/or a device within the drying zone such as a heated pressure roller. For example, the drying zone can include a halogen lamp and resistive heating wire which can each generate heat within a belt roller of a heated pressure roller. Additionally, the number of heating sources can be driven (e.g., powered) by pulse width modulation (PWM) signals

[0010] In some examples, a control cycle can be portioned based on calculated PWM values of each of the heating sources driven by the PWM signals, where a first portion of the control cycle can be associated with a first heating source and a second portion of the control cycle can be associated with a second heating source. For example, during the first portion of the control cycle a halogen lamp can be driven by a PWM signal and during the second portion of the control cycle resistive heating wire can be driven by a second PWM signal. However, in many examples, multiple heating sources can not be driven by the same PWM signal simultaneously due to available power or other constraints.

[0011] In some examples, the imaging device can utilize a RID mode that can utilize a PWM value (e.g., starting PWM value, seeding PWM value, etc.) for increasing a current temperature of the drying zone and/or the number of heating sources in some examples, the PWM value can be a seeding PWM value that can be calculated utilizing a current temperature of the drying zone and/or number of heating sources, a maximum PWM value, a minimum PWM value, and/or a temperature set point for a particular print job. Additionally, the seeding PWM value can be based on an applied voltage. In this way, the seeding PWM value can be implemented at the start of a RID mode and provide more accurate temperatures and power controls, provide fewer temperature over-shoots, reduce media jams, reduce media damage, provide better page to page alignment within a finisher device, lower thermal stress on parts of the imaging device, and/or lower a risk of tripping thermal fuses/cutoffs.

[0012] In some examples, the seeding PWM value can be implemented when a second heating source reaches a threshold temperature while a first heating source is driven by a PWM signal during a first portion of the control cycle. For example, power delivery by a PWM signal to the second heating source can be disabled at a point in time during the control cycle that corresponds to the seeding PWM value being satisfied and re-enabled at a point in time just prior to the end of the control cycle. This can allow the appropriate amount of power to be delivered to the second heating source and can provide fewer temperature overshoots and sags.

[0013] As such, the disclosure is directed to PWM driven heating sources. For example, a device for PWM driven heating sources can include a non-transitory machine readable medium storing instructions executable by a processing resource to: portion a control cycle based on calculated PWM values of a number of heating sources driven by PWM signals, receive a feedback signal from a sensor associated with a second heating source while a first heating source is driven by a PWM signal during a first portion of the control cycle, alter the PWM value for a second portion of the control cycle associated with the second heating source based on the received feedback signal, and apply the altered PWM value for the second portion of the control cycle associated with the second heating source.

[0014] Figure 1 illustrates a memory resource storing instructions for pulse width modulation driven heating sources according to an example in some examples, the memory resource 102 can be utilized to store instructions 104, 106, 108, 1 12 that can be executed by a processing resource. For example, the memory resource 102 may be communicatively coupled to a processing resource which may be a central processing unit (CPU), a

semiconductor-based microprocessor, and/or other hardware devices suitable for retrieval and execution of instructions 104, 106, 108, 112 stored in the memory resource 102 (e.g., in a non-transitory computer readable medium). The example processing resource may fetch, decode, and execute instructions. As an alternative, or in addition to, retrieving and executing instructions, the example processor may include an electronic circuit that may include electronic

components for performing the functionality of executed instructions.

[0015] In some examples, the processing resource may be a plurality of hardware processing units that may cause machine-readable instructions to be executed. The processing resource may include central processing units (CPUs) among other types of processing units. The memory resource 102 may be any type of volatile or non-volatile memory or storage, such as random- access memory (RAM), flash memory, storage volumes, a hard disk, or a combination thereof

[0016] The memory resource 102 may store instructions thereon, such as instructions 104, 106, 108, 112. When executed by the processing resource, the instructions may cause an imaging device to perform specific tasks and/or functions. For example, the memory resource 102 may store instructions 104 which may be executed by the processing resource to cause the imaging device to portion a control cycle based on calculated PWM values of a number of heating sources driven by separate PWM signals. In some examples, a first portion of the control cycle is associated with a first heating source and a second portion of the control cycle Is associated with a second heating source.

[0017] In some examples, the portions of the control cycle can correspond to a quantity of heating sources included within a drying zone of the imaging device. For example, the control cycle can correspond to a quantity of heating sources that are included within a heated pressure roller. A control cycle can be a period in which multiple PWM signals are active, where the period is a time it takes for all PWM signals to complete an on-and-off cycle. The period can correspond to a count value, such as 127. in such example, a count value of 127 can equate to three seconds. Thus, after three seconds the counter value can roll over to zero, starting a new control cycle.

[0018] In an example, where a drying zone includes more than two heating sources, a control cycle can be portioned based on the quantity of heating sources that are driven by the separate PWM signals. In an example where there are two heating sources being driven within the same control cycle, a first heating source can be associated with a first portion of the control cycle and a second heating source can be associated with a second portion of the control cycle.

[0019] Additionally, the control cycle can be portioned based on calculated PWM values of the number of heating sources. For example, a PWM value can be calculated for each of the number of heating sources. The calculated PWM values of the number of heating sources can be based on a start temperature and a set point temperature for the number of heating sources. Furthermore, the calculated PWM values can be proportional to a difference between the setpoint temperature and the start temperature of the number of heating sources. For instance, when there are a number of heating sources the PWM vaiues can be proportional to a difference between a setpoint temperature and a start temperature of each of the number of heating sources. The PWM values may also be determined based on applied voltage.

[0020] In an example where the control cycle has a count value of 127 and two heating sources, the first calculated PWM value associated with the first heating source may be 64 and the second calculated PWM value associated with the second heating source may be 63. Thus, the first portion of the control cycle may be programmed with a PWM value of 64 and the second portion of the control cycle may be programmed with a PWM value of 63.

However, in some examples, no more than one of the number of heating sources can be driven simultaneously during a particular portion of the control cycle. That is, one of the number of heating sources can be driven by a PWM signal during a particular portion of the control cycle. Thus, the first heating source that is associated with the first portion of the control cycle can be driven by a first PWM signal during the first portion of the control cycle (e.g., from zero to 64 counts) and the second heating source that is associated with the second portion of the control cycle can be driven by a second PWM signal during the second portion of the control cycle (e.g., from 64 to 127 counts).

[0021] The memory resource 102 may store instructions 106 which may be executed by a processing resource to receive a feedback signal (e.g., feedback temperature) from a sensor (e.g., temperature sensor) associated with the second heating source while the first heating source is driven by a PWM signal during the first portion of the control cycle. In an example where there are two heating sources, a first sensor can be associated with the first heating source and a second sensor can be associated with the second heating source.

[0022] In some examples, the memory resource 102 can receive a feedback temperature value for a plurality of devices associated with an imaging device. For example, the memory resource can be communicatively coupled to a plurality of temperature sensors that are utilized to monitor a temperature of a corresponding device or area of the imaging device. In some examples, the threshold temperature is a temperature that when exceeded initiates a proportional integral derivative (RID) mode for the heated pressure roller. The RID range can be a range of temperatures at which a RID mode is utilized. For example, the FID range can be a range of temperatures between a threshold temperature and a set point temperature for a heated pressure roller

[0023] In some examples, the temperature sensors can be utilized to monitor a temperature of a number of heating sources within a drying zone of an imaging device. For example, a temperature sensor can be utilized to monitor the temperature of a number of heating sources within a heated pressure roller. In this example, the temperature sensors can be utilized to determine when each of the number of heating sources within the heated pressure roller is at or near a set point temperature. The set point temperature can be a temperature that is set for a particular print job to remove potential distorted properties caused by depositing a print substance on the print media in some examples, the set point temperature can be based on a quantity of print substance that is deposited on the print media and/or a predicted level of distorted properties of the partially dried inkjet media. That is, the number of heating sources within the heated pressure roller may be set to a temperature (e.g , utilize a set point temperature, etc.) that is capable of removing or substantially removing distorted properties from the partially dried inkjet media.

[0024] In some examples, the memory resource 102 can receive a feedback signal from a sensor associated with the second heating source while the first heating source is driven by a PWM signal during the first portion of the control cycle. The feedback signal can provide an indication to the memory resource 102 that the second heating source has reached or exceeded a threshold temperature while the first heating source is driven by a PWM signal during the first portion of the control cycle

[0025] As used herein, a threshold temperature value can be a particular temperature that can trigger an event For example, the threshold temperature can be a temperature when a heat source associated with the drying zone is altered from a ramp up state to a PiD state. In some examples, the ramp up state can be a state when the heat source is generating a maximum or relatively large quantity of heat to bring the temperature of the drying zone up toward the set point in a relatively small quantity of time. In some examples, the heating source can alter from the ramp up state to the PID state when the monitored temperature exceeds the threshold temperature to prevent the monitored temperature of the drying zone from overly exceeding the set point temperature, which can waste electrical power of the imaging device and/or generate errors for the print job.

[0026] The memory resource 102 may store instructions 108 which may be executed by a processing resource to alter the PWM value for the second portion of the control cycle associated with the second heating source based on the received feedback signal. The altered PWM value can be a seeding value. The seeding PWM value can be a starting value for a PWM controller to apply to one or more of the heating sources to alter the temperature of the drying zone and/or heated pressure roller from a current temperature to a set point temperature. In addition, the seeding PW i value can be utilized to prevent the temperature of the drying zone and/or heated pressure roller from significant temperature overshoots (e.g., temperatures that far exceed the set point temperature, etc.), which can increase power usage and/or potentially damage print media.

[0027] In some examples, the memory resource 102 can calculate the seeding PWM value for the PiD mode of the controller for the second heating source based on a linear interpolation between the set point temperature and the threshold temperature or based on a voltage. In some examples, the set point temperature can be based on features of the print job (e.g., quantity of printing substance deposited on the print media, size of the print media, etc.). In some examples, the seeding PWM value for the PID mode can be based on a linear interpolation between the set point temperature for the print job and the determined threshold temperature, which can be based on the set point temperature. As used herein, linear interpolation includes curve setting methods that utilize data points to fill in additional data points based on a determined curve from real data points. In some examples, the linear interpolation can be stored in the memory resource 102 such that received values can be identified and a seeding PWM value can be calculated.

[0028] The seeding PWM value can be between a minimum PWM value and a maximum PWM value for the second portion of the control cycle associated with the second heating source, where the seeding PWM value can be based on a previous PWM value for a previous print job of the imaging device. For example, if the second portion of the control cycle corresponds to counter values 64 through 127, the seeding PWM value for the associated heating source (i.e. second heating source) can be a PWWI value greater than 0 (or a preset minimum allowable PWM seeding value) but less than or equal to 63 that would begin being applied once the cycle counter reaches 64.

[0029] The memory resource 102 may store instructions 112 which may be executed by a processing resource to apply the altered PWM value for the second portion of the control cycle associated with the second heating source. When the monitored temperature of a second heating source has reached or exceeded the threshold temperature while a first heating source is driven by the PWM signal during the first portion of the control cycle, the RID state for the second heating source can be initiated.

[0030] In such example, the RID state can utilize a seeding PWM value to more precisely bring the temperature to the set point temperature of the print job. For example, the seeding PWM value can bring the temperature up to the set point value more quickly without significantly exceeding the set point temperature compared to utilizing a maximum or minimum PWM value That is, a first maximum PWM value can be utilized when the second heat source is in a ramp up state and a second PWM value (e.g., seeding PWM value) can be utilized when the monitored temperature of the second heating source associated with a second portion of the control cycle exceeds the threshold temperature during the first portion of the control cycle, causing the heat source to transition for a ramp up state to a PI D state. Thus, when the temperature of the second heating source is above the threshold temperature while a first heating source is driven by a PWM signal during the first portion of the control cycle, a seeding PWM value for the second heating source can be calculated.

[0031] Additionally, when the monitored temperature of a second heating source has reached or exceeded the threshold temperature while a first heating source is driven by a PWM signal during the first portion of the control cycle, the second heating source can remain enabled during the first portion of the control cycle. That is, the second heating source can remain enabled while the first heating source is driven by the PWM signal. Disabling power delivery to the second heating source while the first heating source is driven by the PWM signal can result in the second heating source not receiving power from the PWM controller until the control cycle counter rolls over back to 0. This may result in the temperature of the second heating source to sag.

[0032] In some examples, the memory resource 102 can disable power delivery to the second heating source based on the seeding PWM value after the source has reached the threshold temperature. Thus, when the second heating source has been on for a time in the second portion of a control cycle corresponding to the seeding PWM value, power delivery can be disabled using a disable bit (e.g., a disable signal). Disabling the power delivery does not interrupt the control cycle. Rather, it can act as a switch to instantaneously turn off power delivery to the second heating source. Allowing the second heating source to remain enabled during the entire second portion of the control cycle when the second heating source reaches the threshold temperature during the first portion of the control cycle can cause the temperature of the second heating source to significantly overshoot. Thus, disabling the power delivery at a time during the second portion of the control cycle that corresponds to the seeding PWM value of the second heating source can prevent the temperature from significantly sagging or overshooting.

[0033] Additionally, the memory resource 102 can re-enable power delivery to the second heating source at a determined cycle count, wherein the determined cycle count is prior to an end of the control cycle. For example, if the second portion of the control cycle ranges from a cycle count of 64 and a cycle count of 127, power delivery can be re-enabled at 126. Thus, before the control cycle returns to zero, an enable bit (e.g , enable signal) can be reinstated, allowing power to once again be delivered to the second heating source at the start of the second portion of the control cycle associated to the second heating source

[0034] Figure 2 is a block diagram of a controller 210 including processing circuitry suitable for pulse width modulation driven heating sources according to an example. Figure 2 illustrates an example controller 210, including a processing resource 214 and a memory resource 202 For example, the controller 210 may include a processing resource 214 which may be a central processing unit (CPU), a semiconductor-based microprocessor, and/or other hardware devices suitable for retrieval and execution of instructions stored in a memory resource 202 (e.g , in a non-transitory computer readable medium).

[0035] The memory resource 202 may store instructions 218 which may be executed by the processing resource 214 to cause the controller 210 to portion a control cycle based on calculated pulse width modulation (PWM) values of a number of heating sources driven by PWM signals, where a first portion of the control cycle is associated with a first heating source and a second portion of the control cycle is associated with a second heating source. As described herein, the control cycle can correspond to a quantity of heating sources that are included within a drying zone (e.g., a heated pressure roller). A control cycle can be a period in which a PWM signal is active, where the period is a quantity of time it takes for a PWM signal to complete an on-and~off cycle.

[0036] In an example where there are more than two heating sources, the control cycle can be portioned based on a calculated PWM value of each of the heating sources. As described herein, the calculated PWM values of the number of heating sources can be based on a start temperature and a set point temperature for the number of heating sources. In some examples, the PWM value can be quantified by a numerical value (e.g., 84, 63, etc.}. Thus, a first heating source that is associated with a first portion of the control cycle can be driven by a PWM signal during the first portion of the control cycle and the second heating source that is associated with the second portion of the control cycle can be driven by another PWM signal during the second portion of the control cycle. The first portion of the control cycle can correspond to a first calculated PWM value and the second portion of the control cycle can correspond to a second calculated PWM value, where the first calculated PWM value is associated with the first heating source and the second calculated PWM value is associated with the second heating source

[0037] The memory resource 202 may store instructions 218 which may be executed by the processing resource 214 to cause the controller 210 to receive a feedback signal from a temperature sensor associated with the second heating source while the first heating source is driven by a PWM signal during the first portion of the control cycle. For example, the memory resource 202 can be communicatively coupled to a plurality of temperature sensors that are utilized to monitor a temperature of the number of heating sources of an imaging device. For example, one temperature sensor can be utilized to monitor a temperature of a first heating source and another to monitor the temperature of the second heating source, within a single heated pressure roller

[0038] The memory resource 202 may store instructions 222 which may be executed by the processing resource 214 to cause the controller 210 to determine if a threshold temperature has been reached by the second heating source based on the received feedback signal. As described herein, the feedback signal can be monitored to determine when the second heating source has reached the threshold temperature in some examples, the threshold temperature is a temperature that when exceeded initiates a RID mode for the second heating source within the heated pressure roller in some examples, the second heating source can reach the threshold temperature while the first heating source is driven by a PWM signal during the first portion of the control cycle

[0039] The memory resource 202 may store Instructions 224 which may be executed by the processing resource 214 to cause the controller 210 to alter the PWM value for the second portion of the control cycle associated with the second heating source based on the determination that the second heating source has reached the threshold temperature. As described herein, the altered PWM value can be a seeding value. The seeding PWM value can be a starting value for a RID controller to apply to the second heating source to alter the temperature of the second heat source from a current temperature to a set point temperature. In addition, the seeding PWM value can be utilized to prevent the temperature of the second heating source from significantly overshooting (e.g., significantly exceed the set point temperature, etc.), and therefore prevent a possible increase in power usage and/or potential damage to print media.

[0040] The memory resource 202 may store instructions 226 which may be executed by the processing resource 214 to cause the controller 210 to apply the altered PWM value for the second portion of the control cycle associated with the second heating source. As described herein, when the monitored temperature of a second heating source has reached or exceeded the threshold temperature while a first heating source is driven by a PWM signal during the first portion of the control cycle, the RID state can be initiated at the start of the portion of the control cycle associated with the second heating source (e.g., at the start of the second portion of the control cycle).

[0041] In such an example, the RID state can utilize the seeding PWM value to more precisely bring the temperature to the set point temperature of the print job. For example, the seeding PV /M value can bring the temperature up to the set point value more quickly without significantly exceeding the set point temperature compared to utilizing a previous PWM value or utilizing a minimum or maximum PWM vaiue for seeding.

[0042] Additionally, when the monitored temperature of a second heating source has reached or exceeded the threshold temperature while a first heating source is driven by a PWM signal during the first portion of the control cycle, the enable bit for the second heating source can remain enabled during the first and second portions of the control cycle. Disabling power delivery to the second heating source for the rest of the control cycle while the first heating source is driven by the PWM signal can result in the second heating source not receiving power until the control cycle counter rolls over from the maximum count value back to 0. This may result in a sag of the temperature of the second heating source. [0043] In some examples, the memory resource 202 can disable power delivery to the second heating source based on its seeding PWM value. Thus, when the time in the second portion of the control cycle corresponding to the seeding PV /M value is reached, power delivery can be disabled using a disable bit (e.g., a disable signal). Disabling the power delivery does not interrupt the control cycle. Rather, it can act as a switch to instantaneously turn off power delivery to the second heating source. Allowing the second heating source to remain enabled during the entire second portion of the control cycle when the second heating source reaches the threshold temperature during the first portion of the control cycle can cause the temperature of the second heating source to overshoot Thus, disabling the power delivery at a time in a control cycle corresponding to the seeding PWM value can prevent the second heating source from significantly sagging or overshooting.

[0044] Additionally, the memory resource 202 can re-enable power delivery to the second heating source at a determined control cycle count, wherein the determined control cycle count is prior to an end of the control cycle. For example, if the second portion of the control cycle ranges from a cycle count of 84 and a cycle count of 127, power delivery can be re-enabied at 126. Thus, before the control cycle count returns to zero, an enable bit (e.g , enable signal) can be reinstated, allowing power to once again be delivered to the second heating source at the start of the second portion of the control cycle associated with the second heating source

[0045] Figure 3 is a block diagram of an imaging device 320 including instructions for pulse width modulation driven heating sources according to an example. Figure 3 illustrates an imaging device 320. The imaging device 320 can be an inkjet imaging device. As used herein, an inkjet imaging device can deposit a print substance (e.g., liquid ink, etc.) on a print media (e.g., paper, etc.). In some examples, the print substance can be absorbed into the print media, which can cause distorted properties (e.g., curl, cockle, etc.) in some examples, the Imaging device 320 can utilize a drying zone 328 to remove excess moisture and/or distorted properties from partially dried inkjet media (e.g., media with deposited print substance from the imaging device 320, etc.). [0046] Figure 3 illustrates an example imaging device 320 that includes a drying zone 328 that includes a heated pressure roller 332. in some examples, the heated pressure roller 332 can be utilized to remove distorted properties from partially dried inkjet media by applying heat and/or pressure on a surface of the partially dried inkjet media in some examples, the heated pressure roller 332 can include a first roller (e.g., top roller, pressure roller, etc.) that can be a solid cylindrical roller that can apply pressure to a first side (e.g., top side, etc.) of the partially dried inkjet media in some examples, the heated pressure roller 332 can include a second roller (e.g., bottom roller, belt roller, heated belt roller, etc.) that can apply heat to a second side (e.g., bottom side, etc.) of the partially dried inkjet media in some examples, the second roller can include a heat source or sources positioned within the second roller to receive a PWM signal from a PWM controller to generate a corresponding quantity of heat based on the received PWM signal. In some examples, the drying zone 328 can be communicatively coupled to a computing device or controller that includes a memory resource 302 and/or processing resource 314. For example, a communication channel can allow a controller (e.g., PWM controller, computing device, etc.) to apply a PWM signal to heat sources of the drying zone 328 (e.g., heat source in first roller, heat source In second roller, etc.).

[0047] Figure 3 Illustrates an example computing device 334 that includes a memory resource 302 storing instructions executable by a

processing resource 314 to cause the imaging device 320 and/or the drying zone 328 to perform particular functions. For example, the imaging device 320 may include a processing resource 314 which may be a central processing unit (CPU), a semiconductor-based microprocessor, and/or other hardware devices suitable for retrieval and execution of instructions stored in a memory resource 302 (e.g., in a non-transitory computer readable medium). In some examples, the processing resource 314 can be communicatively coupled to the memory resource 302 through a communication channel. In some examples, the communication channel can be a physical or wireless connection to allow the processing resource 314 to retrieve and/or execute the instructions stored on the memory resource 302. [0048] The memory resource 302 may store instructions 338 which may be executed by the processing resource 314 to cause the imaging device 320 to calculate PWIV3 values of each of the number of heating sources for a control cycle. The PV /M values, for example, can be calculated in a manner analogous to that previously described in connection with Figure 1.

[0049] The memory resource 302 may store instructions 338 which may be executed by the processing resource 314 to cause the imaging device 320 to portion the control cycle based on the calculated PWM values of the number of heating sources, where a first portion of the control cycle is associated with a first heating source and a second portion of the control cycle is associated with a second heating source. The control cycle can be portioned, for instance, in a manner analogous to that previously described in connection with Figure 1.

[0050] The memory resource 302 may store instructions 342 which may be executed by the processing resource 314 to cause the imaging device 320 to receive a feedback signal from a temperature sensor associated with the second heating source while the first heating source is driven by a PWM signal during the first portion of the control cycle. The feedback signal can be received, for example, in a manner analogous to that previously described in connection with Figure 1.

[0051] The memory resource 302 may store instructions 344 which may be executed by the processing resource 314 to cause the imaging device 320 to determine if a threshold temperature has been reached by the second heating source based on the received feedback signal. The determination of whether the threshold temperature has been reached can be made, for example, in a manner analogous to that previously described in connection with Figure 1.

[0052] The memory resource 302 may store instructions 348 which may be executed by the processing resource 314 to cause the imaging device 320 to alter a PWM value for the second portion of the control cycle associated with the second heating source based on the determination that the second heating source has reached the threshold temperature. Altering a PWM value for the second portion of the control cycle associated with the second heating source can be performed, for example, in a manner analogous to that previously described in connection with Figure 1.

[0053] The memory resource 302 may store instructions 348 which may be executed by the processing resource 314 to cause the imaging device 320 to apply the altered PWM value for the second portion of the control cycle associated with the second heating source. The altered PWM value can be applied, for instance, in a manner analogous to that previously described in connection with Figure 1.

[0054] Figure 4 is a diagram 430 of a control cycle 462 associated with pulse width modulation driven heating sources according to an example. As previously described, the process for PV /M driven heating sources can include portioning a control cycle 462 based on calculated PWM values of a number of heating sources driven by separate PWM signals. For example, a first portion 452 of the control cycle 462 can be associated with a first heating source and a second portion 454 of the control cycle 462 can be associated with a second heating source.

[0055] In some examples, the second heating source can reach or exceed a threshold temperature at a time 456 into control cycle 462 while the first heating source is driven by a PWM signal during the first portion 452 of the control cycle 462. To prevent the second heating source from experiencing a temperature sag, the second heating source can remain enabled until the time in the second portion of control cycle 462 corresponding to its seeding PWM value, rather than being disabled for the rest of control cycle 462.

[0056] As described herein, in response to the first heating source reaching or exceeding the threshold temperature at a time 456 into control cycle 462, a memory resource can alter the PWM value that is associated with the second heating source. The altered PWM value, applied until time 458 into the control cycle, can be a seeding PWM value in some examples, power delivery to the second heating source can be disabled at a time in control cycle 462 that corresponds to the altered PWM value. Disabling power delivery to the second heating source at the time 458 corresponding to the altered PWM value can provide fewer temperature overshoots. Additionally, the memory resource can re-enable power delivery to the second heating source at a time in control cycle 462 corresponding to a determined cycle count value, wherein the time is prior to an end of control cycle 462.

[0057] In the foregoing detailed description of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration how examples of the disclosure can be practiced. These examples are described in sufficient detail to enable those of ordinary skill in the art to practice the examples of this disclosure, and it is to be understood that other examples can be utilized and that process, electrical, and/or structural changes can be made without departing from the scope of the disclosure.

[0058] The figures herein follow' a numbering convention in which the first digit corresponds to the drawing figure number and the remaining digits identify an element or component in the drawing. Similar elements or components between different figures can be identified by the use of similar digits. For example, 221 can reference element“21” in Figure 2, and a similar element can be referenced as 321 in Figure 3. Elements shown in the various figures herein can be added, exchanged, and/or eliminated so as to provide a plurality of additional examples of the disclosure. In addition, the proportion and the relative scale of the elements provided in the figures are intended to illustrate the examples of the disclosure and should not be taken in a limiting sense.

Claims

What is claimed:

1. A non-transitory machine readable medium storing instructions executable by a processing resource to:

portion a control cycle based on calculated pulse width modulation

(PWM) values of a number of heating sources driven by PWM signals, wherein a first portion of the control cycle is associated with a first heating source and a second portion of the control cycle is associated with a second heating source; receive a feedback signal from a sensor associated with the second heating source while the first heating source is driven by a PWM signal during the first portion of the control cycle;

alter the PWM value for the second portion of the control cycle associated with the second heating source based on the received feedback signal; and

apply the altered PWM value for the second portion of the control cycle associated with the second heating source.

2. The medium of claim 1 , wherein the number of heating sources are associated with a drying zone of an imaging device.

3. The medium of claim 1 , wherein one of the number of heating sources is driven by a PWM signal during a particular portion of the control cycle.

4. The medium of claim 1 , wherein the feedback signal is utilized to determine that the second heating source has reached a threshold temperature.

5. The medium of claim 1 , comprising instructions executable by the processing resource to calculate the PWM values of the number of heating sources based on a start temperature and a set point temperature for the number of heating sources.

6. The medium of claim 1 , comprising instructions executable by the processing resource to calculate the PWM values of the number of heating sources based on an applied voltage.

7. The medium of claim 1 , wherein a quantity of portions of the control cycle correspond to a quantity of heating sources.

8. A controller for a drying zone, comprising:

processing circuitry to:

portion a control cycle based on calculated pulse width modulation (PWM) values of a number of heating sources driven by PWM signals, wherein a first portion of the control cycle is associated with a first heating source and a second portion of the control cycle is associated with a second heating source;

receive a feedback signal from a temperature sensor associated with the second heating source while the first heating source is driven by a PWM signal during the first portion of the control cycle;

determine a threshold temperature has been reached by the second heating source based on the received feedback signal;

alter the PWM value for the second portion of the control cycle associated with the second heating source based on the determination that the second heating source has reached the threshold temperature; and apply the altered PWM value for the second portion of the control cycle associated with the second heating source.

9. The controller of claim 8, wherein the altered PWM value is a seeding value based on an applied voltage.

10. The controller of claim 9, wherein the seeding PWM value is between a minimum PWM value and a maximum PWM value for the second portion of the control cycle associated with the second heating source.

11. The controller of claim 9, wherein when the second heating source has been on for a time in the second portion of the control cycle corresponding to the seeding PWM value, power delivery is disabled using a disable bit.

12. The controller of claim 8, wherein the second heating source remains enabled during the first portion of the control cycle.

13. An imaging device, comprising:

a drying zone that includes a heated pressure roller, wherein the heated pressure roller includes a number of heat sources to increase a temperature of the heated pressure roller, where each of the heat sources are driven by pulse width modulation (PWM) signals; and

a computing device comprising instructions executable by a processing resource to:

calculate PWM values of each of the number of heating sources for a control cycle;

portion the control cycle based on the calculated PWM values of the number of heating sources, wherein a first portion of the control cycle is associated with a first heating source and a second portion of the control cycle is associated with a second heating source;

alter the PWM value for the second portion of the control cycle associated with the second heating source based on the determination that the second heating source has reached the threshold temperature; and

apply the altered PV /M value for the second portion of the control cycle associated with the second heating source.

14. The imaging device of claim 13, comprising instructions executable by the processing resource to disable power delivery to the second heating source based on the altered PWM value.

15. The imaging device of claim 13, comprising instructions executable by the processing resource to re-enable power delivery to the second heating source at a time in a control cycle corresponding to a determined control cycle count, wherein the time is prior to an end of the control cycle.