20 amp fire siren 12 volt to 6 volt circuit.

rlhess

Joined Sep 29, 2011
2
If I understand the conversation correctly, it sounds as if the controller is now putting out full voltage with no control. Is that correct?

If so, I'm afraid the output transistor has shorted.

If this shiny chrome siren is as I think it is, it has a DC motor with a commutator and brushes. The coils on the motor when the circuit is broken and remade generate large spikes that semiconductor junctions don't like. One thing you can try and do when you get a new PWM board from the good folks in Vancouver (also discuss this with them) is run some diodes around the output. The most important one is probably a reverse-biased diode across the PWM output. You will see this on relay coils all the time in circuits. This prevents the reverse spike coming from the inductor when the circuit is opened by the PWM transistor from hurting things.

When the brushes open and close, they might also produce reverse transients. Without looking at the waveform on a scope, it is hard to say. I haven't played around with this for many decades.

The positive output might benefit from a diode connected so if the voltage at that terminal goes higher than the supply voltage it will conduct into the supply voltage (to the PWM device.

Again, contact the manufacturer and discuss this. I would have thought they would have put protection diodes in there, but the siren may have spiked to the point of blowing the protection diodes with higher-current pulses than accommodated for in the design.

Just a thought as I was having fun reading about your fun.

Cheers,

Richard
 

Thread Starter

fireftrmike

Joined Sep 15, 2011
24
12 volts in zero out at this time. I'll call Cana Kit Monday. I'll also send them a Email now with specifics. Thank You for your response. .......... Maybe the red light in series would be easier :)
Mike
 

Thread Starter

fireftrmike

Joined Sep 15, 2011
24
Cana Kit is not responding to my email request for help. I hooked up the circuit again today and at this time it has full voltage output only. (It didn't work at all a few days ago.) I guess a phone call is in order. Don't think it's returnable??
 

Thread Starter

fireftrmike

Joined Sep 15, 2011
24
Tried putting a halogen light in series with motor tonight. Light comes on as if the motor is out of circuit. (motor doesn't turn) A closer look at the motor face plate revealed that the motor is a type C. Not sure what that means. Googling "type C motor" didn't come up with anything.
 

Thread Starter

fireftrmike

Joined Sep 15, 2011
24
Spun the motor up and hooked the light in series before it quit turning. The motor quit and the light stayed bright as ever. Never thought anything so simple would..................:)
 

gerty

Joined Aug 30, 2007
1,281
The motor quit, when in series with the light, because it draws much more current than the light.
If you put a headlight bulb in series with a parking light bulb, the parking light bulb would light , and the headlight wouldn't, same theory.
What would've been ideal was to put the speed control at about 1/4 throttle and take it from there. Monitoring voltage and current as you adjust the control.
You mentioned u1 in an earlier post, what is the part number on it?
 

Thread Starter

fireftrmike

Joined Sep 15, 2011
24
I tried pwm kit. Burned it out I guess from feedback? (per rlhess above)
Cana Kit# UK1130 U1# ?

What can I put in series to make this work?

OR.......... I'll just let it scream on 12 volts till it quits then go to plan D. :)
 
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