help with circuit design?

i want to design a control circuit with the given functionality:

1) press the push button and control circuit (the image attached) will power up and give a countdown (approx. 8-10s)

2) once countdown is done trigger a control current of a separate circuit

3) turn the control (the image attached) off.

http://img215.imageshack.us/img215/1176/58072459.p...

parts that needs consideration:

C1 = 47uF to 220uF

latching DPDT relay:

http://www.nteinc.com/relay_web/pdf/R72.pdf

latching push button (still not final, it's too big):

http://www.galco.com/scripts/cgiip.exe/wa/wcat/ite...

N/O DPST relay:

http://www.nteinc.com/relay_web/pdf/R74.pdf

QUESTIONS:

i'm not really sure with it. i have these 2 unknown component that are lock-off devices -- if current goes through the gates, it OPENS, BUT it has to do it EVEN IF THERE IS NO CURRENT FLOWING THROUGH THE ANODE AND CATHODE YET AND MAINTAIN IT FOR AT LEAST 7-10ms ... though i haven't actually heard of such a device, does it even exists

and i'm trying to discharge C1 so for the next cycle it'll work glitch free, and that discharge should also keep the current going so as to let 5ms pass and completely switch the latching relay.

i wanted to change the N/O DPST relay to a solid state device... (a FET, maybe???), one that is still small. what's the lowest voltage that this control circuit can operate reliably (6-9 V??)

one last thing, the "control" in the diagram would typically supply current to a gate in a thyristor, switching a separate circuit.

Update:

@roger:

gee i never thought that TIP32 turns on as it DISCHARGES C1, thought C1 takes about a few seconds to charge causes TIP32 to turn on.

anyways...

i still have to know what are those 2 "diodes".... i don't wanna be reading a whole topic on diodes on wikipedia to figure it out, you see. a specific part number would help tremendously.

2 Answers

Relevance
  • Roger
    Lv 7
    9 years ago
    Favorite Answer

    First you must understand what the circuit in the schematic does and how it works. When the latching push button switch is pressed, it turns on the TIP32 transistor and discharges capacitor C1. The transistor turns on the NO DPST relay. One set of contacts turns on the load, the second contacts via diode D1 energizes the reset contacts of the latching DPDT relay. The latching relay contacts close which causes C1 to charge up keeping TIP32 on until the capacitor is charged. When C1 charges up ( in 10 seconds or so) the NO DPST relay turns off.

    To re energize this circuit again the latching button must be depressed, this in turn again turns on the TIP32 transistor and discharges capacitor C1. The transistor turns on the NO DPST relay. One set of contacts turns on the load, the second contacts via diode D2 energizes the set contacts of the latching DPDT relay. The latching relay contacts open which causes C1 to charge up keeping TIP32 on until the capacitor is charged. When C1 charges up ( in 10 seconds or so) the NO DPST relay turns off. **Note a diode should be place across the N/O DPST relay coil, anode to ground and cathode to the TIP32 collector

    This statement "and i'm trying to discharge C1 so for the next cycle it'll work glitch free, and that discharge should also keep the current going so as to let 5ms pass and completely switch the latching relay." The latching pushbutton discharges the capacitor C1.

    The N/O DPST relay can be changed to a solid state device..see if you can find a DPST relay that can operate around 6 to 9 volts.

    To operate a thyristor use an opto coupler to isolate this circuit from 120 volt AC.

  • lavzon
    Lv 4
    3 years ago

    Use a transistor as a change with a resistor from the provision to the backside and the LED interior the collector alongside with a resistor to the provision. Now positioned the relay touch from the backside to the emitter. whilst the drawer is closed and the touch closes, the transistor will turn off.

Still have questions? Get your answers by asking now.