GB2219701A - Electronic control circuit for garage door and gate operators - Google Patents

Abstract

An electronic control system for an electric motor driven mechanism having two opposing extremes of travel, such as a garage door, where a signal to the motor to open the door is initiated and sustained in operation by a first circuit Q1 and to close the door is initiated by a second circuit Q3 but sustained in operation by a third circuit Q2. Since all circuit states are determined by an alternate-action switch 51a-51c common to all three circuits plus two normal limit switches 52, 53 and a set-reset flip-flop IC1c-IC1d, an opening door can be stopped and started at will or by unlimited types of override sensor switches, or when closing can be reversed to run open at will or by unlimited override switches. If stopped by an override switch the motor will not restart until commanded to. The motor may be a series type motor or an induction motor. <IMAGE>

Description

IMPROVEMENT @IN ELECTRONIC CONTROL CIRCUIT FOR GARAGE DOOR AND GATE OPERATORE This invention relates to an electronic motor control unit used in an automatic garage door or gate operator.

The reouirements of an electronic control circuit for an automatic garage door operator are:1. On application of a normal trigger signal (typically from a Dush button switch or via remote control) the door should always travel in the correct direction. The correct direction is always to run the door open unless the door is alreadv fullv open in which case it will be run closed.

2. When the door reaches the fully open position the motor should stop automaticailv. On receipt of another normal trigger signal the door will run closed and when fullv closed the motor should stop automatically.

1 and 2 above are minimum reouirements. Highly desirable are the following safety features:3. After a first normal trigger signal has caused the door to run open a second normal trigger signal. or in the case of door obstruction a signal from an overload mechanism, should cause the door to stop. The cjoor should remain stationarv when the cause of the obstruction is removed but on application of a further normal trigger signal the door should continue opening.

4. After a first normal trigger signal has caused the door to start closing from the fully open position a second normal trigger signal. or in the case of door obstruction (e.g. by a car) a signal from an overload mechanism, should cause the motor to be reversed so as to re-oDen the door and lift it of the obstruction. When the door is re-opening the safetv requirements of 3 above should apply.

The logic required to satisfv all the conditions of 1-4 above normally result in manufacturers having to invest tens of thousands of pounds in having a custom made large scale integrated circuit (LSI) specially mask programmed for the purpose. Subsequently each IC costs the manufacturer about e2. Those who do not make this investment find a partial solution in using a combination of several 'off the shelf' integrated circuits (I.C.s). In spite of this certain problems are endemic. For example some control circuits will not respond to a normal signal once the door is moving in either direction and some will not respond to overload signals when the door is opening.When the door is closing some, particularly of the LSI type, respond to normal signals by simply stopping the motor and to overload signals by reversing the motor. This is because the signals come from different sources and are processed independently, since if an overload signal lasts for more than a second or so the l.C.is programmed to close down and can only be reset by switching off the power momentarily. A common problem is that due to variations in the inertia of certain doors an obstruction on closing will result in the door stopping and remaining stationary owing to lack of recovery time and because of the timing element the control circuit senses not only an obstruction on closing but also an obstruction on opening.The cure is to set a low overload limit to ensure fast resetting of the overload mechanism following motor reversal. However this is aLso detendet on how well the installer counterbalances the door and places the setting of this limit outside the control of te menufacturer. For this reason some control circuits are designed mereiv tn stoD the motor or obstruction whichever direction the door is travelling The control circuit to be described not only satisfies all the reouirements of 1-4 above and resolves the reversal problem described above but employs only one 'off the shelf' CMOS I.C. presently costing typically 15 Dence and in larder auantities much less.

According to the present invention there is provided an electronic control system of the kind specified where a signal to rotate the motor in one direction is initiated and sustained -by a first circuit and in the opposite direction is initiated by a second circuit but sustained in operation by a third circuit.

A specific embodiment of the invention will now be described by was of example with reference to the accomtanvin drawing in which: Figure 1 illustrates the control circuitry and truth tables for the logic.

In order to concentrate on the more novel features certain sections of the circuitry. which are subject to variation in any case. are not illustrated in figure 1. One such section is the low voltage power supplv circuit. This can be a battery or it can be derived from the secondary winding of a conventional mains power isolating transformer. the ac voltage being rectified and smoothed and is annotated in figure 1 as t'V. This voltage powers the relay coils and transistors together with a voltage regulator circuit suitable for powdering the CMOS IC and providing protection from eiectrical spikes generated by relay and motor operation and is annotated Vr..Motor circuitry will be discussed later but by wav of explanation when NPN transistor Q1 (first circuit) is forward biased. relay RLA is energised and its contacts close to transmit power to the motor which rotates in a direction such that the door runs open. When relav RLB is energised its contacts close to transmit power to the motor which rotates in a reverse direction such that the door runs closed. RLB can onlv be energised via NPN transistor Q3 (second circuit) but only momentarilv because current is transmitted via capacitor C3. resistor R9 being of high resistance and unable to Provide even adequate holding current and is there merely to ensure complete discharge of C3 when Q3 switches off.Once RLB is energised via Q3,only a forward biased NPN transistor Q2 (third circuit) can supply, via resistor R8, sufficient holding current, but not energisation current, to keep RLB energised.

RLA and RLB contacts are not shown since the number will vary according to the type of motor being controlled. Diodes D1 and D2 act as conventional switching spike suppressors for RLA and RLB respectively. ICI is a proprietory CMOS 4001 which consists of four 2 input NOR gates. the Dins being numbered 1-14, pins 7 and 14 (not shown) connecting the IC to the zero rail annotated OV and regulated positive voltage rail annotated Vr respectively. Gates ICIa and ICIb are cross couPled for bi-stable operation and together with resistors R1, R2 and capacitor Ci form an alternate-action switch which changes the outputs of both gates every time a mechanical switch Si is closed(see truth table).

Capacitor C2 is a sDike suppression filter. Typically Sla is a oress-to-make manual pushbutton switch. Slb is a normally open (N.0.) relav contact controlled by a remote control receiver and Sic a F.0. switch or relav contact which is caused to close on motor overload. Since ail these switches arp common and thus effectively act as a single signal source subsequent processing is minimised whilst maintaining flexibility since other common N.O. switches can optionally be added to provide anv safety override feature.Other proprietorv alternate- action switches are available as will be Explained. Cates ICIc and ICId are cross-connected to form a set-reset (RS) flip-f lop. resistors R5 and R7 alwavs providing at least one source of bias to pins 9 and13 respectively (see truth table in fig 1). Resistors R3, R6 and R10 limit the current to the base of transistors Q1, Q2 and Q3 respectively. Resistors R4 and R5 provide further bias to Q1 and Q2 respectively.S3 is a normallv closed (N .0.) limit switch, typically a microswitch. operated bv the door or its motor mechanism when the door is within a few centimeters of its fully closed position. S2 is a change- over (C/O) limit switch. typically a microswitch, operated bv the door or its motor mechanism when the door is within a few centimetres of its fuilv open position. For ease of descriDtion if in the text S2 is described as 'closed' it means that common terminal a is in contact with terminal b as shown in fig 1 and if described as 'open' it means that common terminal a is in contact with terminal c. Meanwhile any pin number mentioned refers to those of the IC.

Fig 1 illustrates the circuit configuration with the door closed. Pin 4 is presently high and pins 3 and 11 are low. Applying a normal trigger signal by Dressing pushbutton S1a. or operating a remote control so that Slb cioses momentarilv. sends pin 3 high and via S2 and R3 biases Ot into conduction energizing RLA whereupon motor rotation opens the door. Once the door has opened a few centimetres S3 cioses but does not affect operation. If whilst the door is opening an obstruction occurs causing Sic to close. or a normal trigger signal is given causing either Sla or Sib to close momentarilv pin 3 goes low.

This removes base current to Ql which switches off, RLA de-enerxises and the motor and door stop. Meanwhile pin 4 woes high but does not affect motor operation since Q2 cannot energise RLB as already explained. Subsequent removal of an obstruction merelv re-oDens Sic but nothing happens since pin 3 still remains low. Application of another normal trier signal once more sends pin 3 high and the motor re-commences to run the door open. When fullv open S2 'opens' which removes base current to Q1 and this as before stops the motor.

To close the door, application of a normal trigger signal sends pin 4 high and pin 3 low. Pin 4 provides base current to Q2 which switches on. Simultaneously pin 9 goes high and pin 13 goes low outputting a high from pin 11. Note this is the only time in the whole door cycle pin 11 outputs a high. This provides base current to Q3 which switches on. its momentary current flow supplementing that of Q2 in order to energise RLB. Note the same object can be achieved by dispensing with C3 and reducing the resistance of R9 such that to energise RLB requires the additional current supplied bv Q2 via R8. However the present arrangement has the advantage that full energisation current only has to be provided for a few milliseconds. Since RLB is now energised the motor runs in the reverse direction to close the door.Once the door has closed a few centimetres S2 'closes' but other than pin 11 going low and removing base current to Q3, which switches off, motor operation is unaffected because sufficient holding current is supplied via R8 to keep RLB energised. Under normal circumstances when the door is fullv closed 53 opens and removes base current from Q2 which switches off, RLB de-energises and both the motor and door stop. Even if 53 was to reclose nothing would haDpen since as alreadv explained Q2 cannot energize RLB on its own and pin it is still outputting a low. If on the other hand whilst the door was closing an obstruction occurs.

for example by a car or e chilà 's toy causing Sic o. c1ose. or a normai trigger signal is given causing either Sia or Slb to ciose momentarily. pin 4 wiil go low de-energising RLB and thus the motor. Meanwhile pin 3 will go high and via 52 and R3 bias Q1 on thus energizing RLA and the motor will run the door back open whether or not Sic re-opens or not. Once the door has been lifted off the obstruction Sic would normally open allowing the door to be stopped either bv a normal trigger signal or overload whilst opening.Even in the unlikely event of Sic not re-opening the motor will still stop when the door is fully open by virtue of 52 'opening' thus removing base current from Qi. If on the other hand the obstruction is due to a mechanical failure :lamming the mechanism and preventing the motor rotating in either direction a mechanical clutch (not shown) will operate.

Additional protection for a stalled motor will vary according to the type. In the case of a series type motor, current will increase very rapidly blowing a fuse in the motor circuit (not shown). In the case of an induction motor which can often afford to stall for a minute or so without overheating a simple timer can be incorporated through the use of AND gates (not shown) to terminate current flow to Q1 or Q2 as appropriate 30 seconds after initiation. This typically eauates to the time it normallv takes the motor' to close and re-oren the door plus 50%.

Typically when the garage door is opened a courtesy tight iliuminates whilst the door is oDen. This too can be incorDorated in the Dresent circuit by employing an extra transistor (not shown) which receives its base current directly from pin 3 of ICla which in turn energises its own relay operated light.

Although throughout, the controlling of a garage door has been described, the same circuit can be applied to the controlling of a gate operator. window opener. curtains or indeed any electrical mechanism which has two opposing extremes of travel.

There are several variations to the circuitry described besides those alreadv mentioned and these will now be mentioned. The circuit can be made to function by using negative logic. This entails using PNP transistors, directly substituting four 2 input FAZED gates for IC1 (e.g. proprietary CMOS 4011 or 4093) and reversing the bias polarity through R4, R5 and R7. Thus for example the door opening cycle will commence when pin 3 goes low providing base current to Q1.When the door is fully open and a normal signal is given for pin 4 to go low this will be the only time pin 11 will output a low and so energise RLB via Q3. Similarlv a CMOS 4013 dual D flip-flop can be used and each flip-floD can be substituted for ICla/IClb and IClc/ICid respectively.

Whilst the inputs to each flip-flop has to be conditioned use of a 4013 does allow for S1 to be a non-mechanical switch which can be an advantage where such switches are required.

In certain circumstances it can prove to be expedient to substitute one or both relays RLA/RLB with transistors. silicon controlled rectifiers. triacs or other types of switches and it may also be necessary for both switches or relays to be operated at the same time in one direction of motor operation such as for example where one relay only operates to reverse the polarity to the motor and the other is common and completes the circuit..

Claims (8)

1. An electronic control system for an electric motor driven mechanism having two opposing extremes of travel where a signal to rotate the motor in one direction is initiated and sustained in operation bv a first circuit and in the opposite direction is initiated by a second circuit but sustained in operation by a third circuit.

2. An electronic control system as claimed in claim 1 where operation of a first limit switch at the first extreme position of the mechanism will deenergise the first circuit and the motor circuit and operation of a second limit switch at the second extreme position of the mechanism will de-energise the third circuit and the motor circuit.

3. An electronic control system as claimed in any preceding claim where the second circuit can only be energised at the first extreme position of mechanism travel, the first circuit can be energised at any other position of the mechanism and the third circuit can be energised at all positions of the mechanism except for the second extreme of travel..

4. An electronic control system as claimed in any preceding claim where the first,second and third circuit is each capable of being energised due to the actuation of the switch common to all three.

5. An electronic control system as claimed in any preceding claim where the second circuit is energised by an RS flip-flop.

6. An electronic control system as claimed in any preceding claim where with motor rotation being sustained by the first circuit, actuation of the common switch will de-energise the first circuit and the motor circuit in spite of energising the third circuit.

7. An electronic control system as claimed in any preceding claim where with the second circuit de-energised and motor rotation being sustained by the third circuit, actuation of the common switch will de-energise the third circuit and energise the first circuit which will initiate and sustain motor rotation in the opposite direction.

8. An electronic control system of the kind specified arranged and adapted to operate substantially as hereinbefore described with the reference to and as illustrated in the accompanying drawing.