GB2140986A - Switching of cyclic and general d.c. devices by a self-commutating- avalanche-device or interval-timer circuit - Google Patents

Abstract

The circuits allow the switching on of a d.c. load for a certain period, which said period is determined either by a time-control means controlling a series-pass means, or by the changing load characteristics of a cyclic load itself which controls a gate-controlled avalanche means; the automatic turning off of said load at end of timing period; the reset of said control means or said avalanche means. Said avalanche means controls cyclic loads, i.e., loads whose current is reduced at or near end of cycle period to below holding current of said avalanche means. Said interval time-control means controls all types of d.c. loads, and may comprise either an RC means, or a monostable means. Both avalanche and time-control means may be used to control a touch-enabled audio-visual canary toy or novelty device. Said avalanche means may be used to turn off a load, such as an indicator lamp, upon change in resistance of sensor, e.g., a thermistor, LDR, etc. <IMAGE>

Description

SPECIFICATION Switching of cyclic and general d.c. devices by a self-commutating-avalanche-device or intervaltimer circuit Background of the invention The present invention relates mainly to various devices which go through one cycle of their performance, especially an audio-visual toy, and to the various circuits which control the turning on of said devices, especially by touch, and theirturning off after completion of said cycle.

The two means presented for turning on said devices, viz., via an SCR or via an interval-controlled series pass transistor are known; however, it is thought that the additional means enabling touch turn-on with either of the above is novel. Furthermore, it is thought that the turn-off after an end of a cycle is also novel, in that, for example, SCR controls usually are used to turn on a device, with no means for automatic turn-off (except forced commutation or manually breaking the circuit). Specifically, it is also thought that the audio-visual canary toy which is activated by touch, which goes through a cycle consisting of singing, warbling and chirping, and which turns itself off automatically, is novel.

It should be mentioned that an electronic circuit duplicating the sound of a canary was exhibited in the 1970 Expo in Japan, as mentioned in "Constructors Manual of Electronic Circuits for the Home," Babani Press Publ. No. 15, London. Said circuit, however, was controlled by a mechanical switch, and, due to the astable multivibrator used in it, did not shut off automatically, but repeated the canary's song after turning off. The basic sound-producing circuit was used, with some modification, in this invention.

Summary of the invention It is therefore an object of this invention to provide a circuit for turning on a cyclic device, and for its automatic turn-off at, or near cycle end; It is also an object of this invention to provide a circuit for an audio-visual canary toy or doorbell, controlled as above; It is a further object of this invention to provide circuits for touch-controlled devices, as above; A main object of this invention is to provide circuits for a touch-operated audio-visual canary toy, as above; Another object of this invention is to provide further novelty devices based on the above audiovisual canary toy, such as an air-humidity-change or moisture-change indicator, and an incoming call signaller;; One more object of this invention is to provide self-commutating SCR (or other gate-controlled avalanche-device) circuits whereby variable-resistance sensors control device turn-off; A final object of this invention is to provide simple interval-timer circuits for any d.c. load.

As mentioned, there are two means of turning on and off the cyclic or other device: via an SCR (or other suitable gate-controlled avalanche device); or, via an interval-controlled series pass transistor.

A) The SCR means of turning on and off a cyclic device makes use of the known properties of the SCR, which, at given operating voltage and tempera ture has a fixed value of necessary minimum gate current: provided by latching current and holding current, where the cyclic device varies in current consumption with time, from an initial value, not lower than the latching current, to a minimum, so that, since the load current drops below said minimum at the cycle end, the device turns off.

The associated touch reset control has currentamplifying means to fire the SCR.

B) The series-pass-transistor means of turning on and off a cyclic, or non-cyclic, device utilizes a pass transistor in series with a load and d.c. power source, the base of which transistor is controlled by any time-control means which will feed the base sufficiently to saturate the transistor for the timing interval, and then remove base feed, either abruptly, or gradually, until a negligible base current flows, a reasonable time after the end of the timing interval.

Also present is a reset means to restart the timing interval.

One embodiment utilizes an RC time constant passing steadily-decreasing current via the base of the pass transistor as the timing capacitor charges, until the base current is insufficient to allow enough current to pass to the load, turning off the device.

The device is reset by discharging said timing capacitor, allowing turn-on.

A second embodiment uses the output of a monostable multivibratorto turn on the said pass transistor for the timing period. Here, reset is accomplished by pulling down the base of the stable-output transistor.

As opposed to the self-commutating SCR circuits mentioned, here, the load current need not drop to a minimum before turn-off.

The associated touch reset controls have currentamplifying means to discharge the timing capacitor, orto pull down the proper monostable transistor base, turning on the pass transistor.

Brief description of the drawings Figure 1 General invention principle for selfcommutating manual-reset SCR embodiment.

Figure 2 Electronic-canary embodiment with various reset means.

Figure 3 Electronic canary and series pass transistor.

Figure 4 Pass transistor timer controls and resets.

Description of the preferred embodiments Figure 1 shows the general invention principle for the self-commutating manual-reset SCR embodiment. In Figure la, the load of SCR 13 is impedance 2, powered from d.c. power source 14, in series with variable impedance 1.Assuming impedance 1 of low initial value, when N.O. switch 27 is momentarily closed, gate is fired via safety resistor 24. Load 2 will be powered as long as impedance 1 in combination with load 2 admit current not less than minimum necessary holding current. If, for any reason holding current drops below said minimum, the SCR will commutate.

For example, variable impedance 1 may be a variable-resistance sensor, such as a thermistor or an LDR, and load 2 might be an indicator lamp, so that, if a change in variable measured (heat; cold light;) took place after the SCR were fired, the device would turn off, even though the variable returned to the former state. Only a combination of normalvariable state and resetting the SCR via switch 27 would reignite the lamp.

Variable impedance 1 may also be any transistor (bipolar, FET, etc.), or combination of transistors, etc., which has initial means for turn-on art a level admitting minimum latching current, and means for reducing current admittance to below holding current. Figure 1 b is a detail of impedance 1 of Figure la. Impedance 1c may be an LDR,thermistor, etc., while impedance 1 b is a resistor, or vice versa. Or, impedance 1b may be some other means of controlling and reducing pass transistor la admittance.

A hold-over capacitor may be connected across SCR gate and cathode to hold it over for short current excursions below minimum holding current.

It should be noted that "SCR" 13 may be any gate-controlled avalanche device with distinct latching and holding currents, either instrinsic, or designed, such as GTO, SCS, regenerative switch, etc., considering load-current capability.

Figure 2a is the circuit diagram for the electronic canary and its SCR control, while Figure 2b - e are various gate-firing means. Operation is as follows: Transformer 2 (miniature output type), transistor 1 a, and feedback capacitor 4 form a blocking oscillator, the oscillation frequency of which is controlled by the voltage, feedback current through resistor 8, and the current through transformer 7 (input of miniature driver type), which latter saturates with increasing current, lowering its inductance. The two time constants 6 - 9, and 5 - 10, determine the above factors. The 2 LEDs 18 and 19 connected in series with the main load and the SCR are the canary's "eyes". Time constant 15 - 16 is included to allow for parts of the cycle when the load current might drop slightly below the minimum holding current, in the case of less-gate-sensitive SCRs.Resistor 17, on the other hand, may be arbitrarily used if the minimum load current is above the holding current, to ensure turn-off. Both means may be used together, one preventing premature turn-off, the other ensuring turn-off at, or near, the cycle end. Capacitor 20 improves audio-visual operation.

Power source means 14, which may be a 9-volt battery, supplies power via resistor 16 and SCR 13 to the load, when the gate is fired, starting the cycle, which consists of three parts: a descending whistle, or song; a warbling sound; a chirping sound. The duration and quality of the warbling sound are very sensitive to the setting of trimmer 8, and somewhat to the setting of trimmer 5 - typical values were about 300 ohms 27 kohms, respectively. A lower setting of trimmer 8 produces a cricket-like sound, after the initial whistle. Capacitor 11 may be arbitrarily used to improve sound.

Figure 2b shows the touch control forthe SCR, where the minute current passing via the fingers from the contacts 26 to 25 is amplified by currentamplifier means, transistor 23, and passes amplified current to the gate via contact 21; resistor 24 limits gate current in case said contacts are shorted.

Figure 2c shows pushbutton means for firing the device, as does Figure 2d; in the latter case, no current-limiting resistor is necessary, as firing current comes from SCR anode only until SCR turns on.

Figure 2e shows a possible circuit for use when momentary indication of pushbutton use is desired.

as for a doorbell control - here, the 2 LEDs 18 and 19 would be omitted.

Figure 3 shows the circuit diagram for the electronic canary (identical to that in Figure 2a), the LED "eyes," the series-pass-transistor means, and power supply for the second control method. LEDs 18 and 19 and series -pass transistor 13 return the current to the negative of the power supply (e.g., a 9-volt battey). Canary circuit operation is as above.

Said pass transistor is controlled by input to its base, via limiting resistor 24, at point A. Resistor 17 reduces leakage current. Capacitor 30 stabilizes circuit operation, and resistor 35 limits its current on turn-on.

Figures 4a - b illustrate two timer controls and resets for the series-pass-transistor control means of Figure 3. In Figure 4a, current flows to transistor 13 (Figure 3) base via time constant 24 - 29, thereby turning on said transistor until capacitor 29 is almost charged to the voltage of power supply 14. Said time-constant action should be approximately equal to the cycle duration, or slightly greater. Transistors 31 and 32 are a Darlington pair which discharges said timing capacitor 29 when contacts 25 and 26 are touched, via current-limiting resistor 33, thereby resetting the device. Resistor 34 limits the leakage due to the input transistor of the pair, 32.

In Figure 4b, when monostable multivibrator 36 is reset, e.g., by touching touch-reset means (as above), the stable transistor turns off for the timing interval, so that its output is high, and said high output turns on the pass transistor 13. The monostable should have very-low quiescent current, so as not to drain the battery. A MOS device might be used here.

One prototype of the audio-visual canary toy was assembled in a plastic sphere of 9 cm diameter, having a flattened bottom which allowed standing.

The two LED "eyes" are about 60 spherical down from the top, and are green, but might also be yellow, etc. These LEDs are set in black grommets.

The two metal contacts are on the top ("head"), but may have been put in place of the "beak". There are perforations at the bottom of the device for the sound to exit from the minature loudspeaker, or other transducer there. There is a recess for the battery,, the off-mode drain of which is minute.

Obviously, differently shaped containers might be used, and different sounds, animal or otherwise, can be included in such a device.

The above-mentioned audio-visual toy may, by slight modification, serve as the basis for the following novelty devices: 1) By connecting the contacts 25 and 26 of Figure 3 or Figure 4 to a material, such as a plastic, the reistance of which is reduced upon water absorption, the device can serve as an air-humidity-change indicator, or to signal any other moisture change; 2) By connecting the contacts 25 or 26 above to a loop of wire, electromagnetic waves may be received, e.g., from a doorbell or from a called telephone, the device signalling the arrival of a visitor, or of an incoming telephone call.

It is thought that such an audio-visual device as the canary toy might be useful for treating the retarded, autistics, etc.

Claims (30)

1. In combination: A gate-controlled avalanche device with distinct latching and holding currents; A d.c. power source means; A cyclic load, where said load comprises at least: first main load means for admitting initial current, which said initial current is not less than said avalanche-means latching current; and, second means for changing admittance ofcurrent to final value below said avalanche-means holding current, whereby avalanche means commutates naturally; and, A reset means wherewith commutated avalanche means can be refired, starting a new load cycle.

2. A circuit according to Claim 1 wherein said gate-controlled avalanche device is an SCR.

3. A circuit according to Claim 1 wherein a time-constant means is part of said load, whereby correction for low gate sensitivity during cycle is attained.

4. A circuit according to Claim 1 wherein said avalanche gate-cathode is shunted with resistance, whereby correction for high gate sensitivity at cycle end is attained.

5. A reset means according to Claim 1 comprising a silicon-transistor or other low-leakage currentamplifier means whereby current applied to base of said transistor-ampifier means causes amplified current to flow via avalanche device gate whereby said avalanche device fired.

6. A self-commutating manual-reset means according to Claim 1 where said second means is one of the group of variable-resistance sensor means comprising: an LDR; and, a thermistor.

7. Aself-commutating manual-reset circuit according to Claim 6 wherein said sensor means is connected in series with said load, said SCR or other avalanche means, and said d.c. power source means.

8. A circuit according to Claim 1 wherein said second means is a series-transistor means the base of which is controlled by a control means, said control means causing series-transistor means to decrease in admittance of load current until said load current drops below said holding current.

9. A circuit according to Claim 1 wherein said first main-load means is an indicator lamp.

10. A circuit according to Claim 8 wherein said control means is a frequency-changing means, whereby feedback to said base is decreased by impedance means in series with said base.

11. An interval timing circuit for connecting a device load to a d.c. power-source means, and disconnecting said load from said power source at end of desired period comprising: Series-pass-transistor means connected between load and said power-source means allowing said load current to flow when said transistor saturated; Time-control means wherewith base of said passtransistor means is directly fed with sufficient current to saturate said transistor for timing interval, said timing interval being esseentially equal to desired on-time; and, Reset means, whereby said time-control means will start timing a new timing interval, again turning on said pass transistor.

12. A circuit according to Claim 11 wherein said device is cyclic.

13. A reset means according to Claim 11 comprising a silicon Darlington-transistor current amplifier means or follower-pair means of two or three members, or other high-input-impedance, hig h-hFE, low leakage means, whereby current applied to base of input transistor of said Darlington amplifier means causes reset means to start new timing interval.

14. A circuit for connecting a device load as in Claim 11 where said time-control means is a timeconstant means whereby charging capacitor of said means provides exponentially-decreasing base excitation of said pass-transistor means for essentially cycle duration, saturating said transistor, until said capacitor essentially charged, and where said reset means discharges said timing-capacitor means, resetting device.

15. A circuit for connecting a device load as in Claim 11 where said time-control means is a monostable-multivibrator means, whereby pass transistorturned on by said multivibrator output during timing interval, and where said reset means pulls down output-transistor base, re-starting timing period.

16. A circuit according to Claim 1 or 11 wherein said first main-load or load means is an audiosimulating means.

17. A circuit according to Claim 16 wherein an audio-visual device is attained by connecting visualindication means in series with said main-load or load means whereby load current flows via said visual indication device and whereby changes in load current during device cycle indicated.

18. A circuit according to Claim 5 or 13 wherein input of said reset means is activated via touchcontact means.

19. A circuit according to Claim 1 or11 wherein said reset means is a suitably-connected mechanical-switch means in series with suitable currentlimiting resistance means.

20. A circuit according to Claim 19 wherein a visual-indication means included in series with said mechanical-switch means whereby momentary contact indicated.

21. A circuit according to Claim 17 whereby said reset means acitivated by touch-contact means.

22. A touch-activated audio-visual canary toy according to Claim 17 where said audio-simulating means load is a circuit simulating canary sounds, where said visual-indication means comprises two LEDs of proper color parallely connected in circuit, which said LEDs also serve as canary's eyes.

23. An electronic canary doorbell according to Claim 16 wherein said audio-simulating means load is a circuit simulating canary sounds.

24. A circuit according to Claim 17 whereby said reset means is activated by increased moisture content of moisture-absorbing material, said absorbing material having lowered resistance when more moist, and said absorbing material connected to input of said reset means.

25. A circuit according to Claim 17 whereby said reset means activated by electromagnetic signal received by wire-loop means at input of said reset means.

26. A device according to Claim 24 with additional on-off switching means to turn device off after signalling excess moisture.

27. An audio-visual electronic canary novelty device according to Claim 24 or 25.

28. A circuit for connecting a cyclic audio-visual canary toy or novelty device to a d.c. power source and disconnecting said load from said power source at essentially end of cycle period comprising: Audio-visual canary-circuit load; Series-pass means connected between said load and said power-source means allowing said load current to flow when said series-pass means closed; Time-control means whereby input of said seriespass means made high during said time interval, said timing interval being essentially equal to said cycle duration; and Reset means, whereby said time-control means will start timing a new timing interval, again turning on said pass means.

29. A self-commutating manual-reset circuit sub stantial ly as described herein with reference to Figures 1 - 2 or a connecting circuit substantially as described herein with reference to Figures 3 - 4.

30. An integrated circuit incorporating any of the above means.