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Need a timer diagram?

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BTW, I did assembly it on a protoboard and it didn't do anything. The relay never tripped.

Verify the lead configuration of the transistors by looking at its datasheet. Also, the polarity of your diodes, and the polarity of the capacitor (your Sim shows a non-polar one, but 100uF will be polarized). Some relays have flyback diodes built-in, so their coil polarity is important. Also, you didn't say what the coil current of the relay is. It might be too high for the drive transistors. Otherwise, double and triple check your wiring. Highlight lines on a schematic as you verify each connection.

Ken
 
Duffy,

After taking another look at your circuit, I also don't see a discharge path for the capacitor after the power is removed. Does it just depend on leakage?

Ken
 
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Verify the lead configuration of the transistors by looking at its datasheet. Also, the polarity of your diodes, and the polarity of the capacitor (your Sim shows a non-polar one, but 100uF will be polarized). Some relays have flyback diodes built-in, so their coil polarity is important. Also, you didn't say what the coil current of the relay is. It might be too high for the drive transistors. Otherwise, double and triple check your wiring. Highlight lines on a schematic as you verify each connection.

Ken

Specs on the relay are

coil voltage nominal 12vdc max 15.6vdc
coil current 30ma
coil resistance 400 ohms +-10%
pickup/dropoff 9.0/.06vdc
 
Duffy,

After taking another look at your circuit, I also don't see a discharge path for the capacitor after the power is removed. Does it just depend on leakage?

Ken

??? I do not know.. sorry.

BTW, how much current can this circuit tolerate. As the source is 12vdc 2amps.
 
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Duffy,

After taking another look at your circuit, I also don't see a discharge path for the capacitor after the power is removed. Does it just depend on leakage?

Ken

No, it depends on Vcc going to ground. That's why I mentioned adding the 1k resistor across the power supply. D1 discharges it, and bypasses the timing resistor for a quick reset on power off.
 
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OK, I couldn't keep away from the bench. Duffy's circuit works as advertised...but it takes a long time for the circuit to reset after power-down...the relay will dropout at power-down, but will pickup immediately on power-up.

Ken
 
Depends on the size of the filter caps. OP said once an hour, so it shouldn't be a problem.
 
No, it depends on Vcc going to ground. That's why I mentioned adding the 1k resistor across the power supply. D1 discharges it, and bypasses the timing resistor for a quick reset on power off.

The 1K resistor make sense, because if the +12v is disconnected by a switch, as opposed to a power supply being shut off, there is no discharge path through the transistors' collectors to ground (to D1 or R1/R2).

ken
 
OK, I couldn't keep away from the bench. Duffy's circuit works as advertised...but it takes a long time for the circuit to reset after power-down...the relay will dropout at power-down, but will pickup immediately on power-up.

Ken

That's kinda what I am looking for, but i need the relay to fire at power on and go for about 15 seconds, then off, after 60 seconds power will be removed at which time everything needs to reset. and wait for another hour before repeating.
 
The 1K resistor make sense, because if the +12v is disconnected by a switch, as opposed to a power supply being shut off, there is no discharge path

Yes, originally I was assuming there were other things on the 12V supply that would discharge it (because of the 60 second dwell time) but now I see that's just a minimum setting for the timer.

Zone97, what are you making with this? I was guessing a fish pump or a plant-watering device.
 
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Yes, originally I was assuming there were other things on the 12V supply that would discharge it.

OP, what are you making with this? I was guessing a fish pump or a plant-watering device.

That is correct, the +v will be connected to circuit and a pump. The relay on its 'NO' side will switch the ground, which is attached to -v of the pump.
 
Very cool! Hope the frog appreciates the effort. Can you water the terrarium without misting up the glass and obscuring the view?
 
Very cool! Hope the frog appreciates the effort. Can you water the terrarium without misting up the glass and obscuring the view?

the misting jets I use, are more like foggers. I have a fan in the front of the terrarium blowing down which helps keep the front from fogging. I'll attach an image.
 

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Its actually a universal water pump for the sprayer in your car, its connected to a water tank, to keep a terrarium watered. I have live plants and tropical geckos and a frog.

Have you tried using the windshield washer pump? I tried using these for an automatic Christmas tree stand watering system. All the replacement ones from the auto parts stores have nylon bearings. These are made to run only for "very" brief periods. I tried several brands and they all melted the bearings trying to refill an half an inch or so of water in the stand.

Ken
 
Have you tried using the windshield washer pump? I tried using these for an automatic Christmas tree stand watering system. All the replacement ones from the auto parts stores have nylon bearings. These are made to run only for "very" brief periods. I tried several brands and they all melted the bearings trying to refill an half an inch or so of water in the stand.

Ken

That's what it is... A washer sprayer. and hence the need to only run it for 15 seconds, every hour or so.. :)
 
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Oh man is this weird - a guy at work was showing me that exact temperature and humidity gauge not three hours ago.
 
So with the motor and wiring in mind, do i need to do anything else to the circuit. As I now have batteries and will try to build the circuit again.
 
Ok built it on a protoboard, all but the motor is connected. When power is applied, the relay turns on but never turns off? It will if i remove power.
 
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