Need a timer diagram?

[zone97]

Guys I appreciate all the help, but I scrapped the IDEA of this working, and hunted, and found a circuit online. I built it but, darn it if it doesn't do the same thing the other one does. (when power is applied the relay trips but does not release.) This time I have a diagram. I built it as it is listed, the only difference is pin 2 in not on a switch it is tied directly to ground. I need this to work using the power as the switch. When power is applied, it triggers the relay for xx seconds, and stops. Resets when power is removed and reapplied. Thanks for the help.

**broken link removed**

Parts

R1 1 1 Meg Pot
R2 1 10 K 1/4 Watt Resistor
C1 1 10uf 25V Electrolytic Capacitor
C2 1 0.01uf Ceramic Disc Capacitor
D1,D2 2 1N914 Diodes
U1 1 555 Timer IC
RELAY 1 9V Relay

 

[duffy]

I built it as it is listed, the only difference is pin 2 in not on a switch it is tied directly to ground.

That's a pretty big difference. Pin 2 is the trigger. It's active low. It drives a simple RS flip-flop and has priority over Thres.

Not going to work that way.

For what you are trying to do, a 555 is more trouble than it's worth. You need one crummy transistor with a cap and a diode and a couple of resistors on the base.

 

[zone97]

That's a pretty big difference. Pin 2 is the trigger. It's active low. It drives a simple RS flip-flop and has priority over Thres.

Need to tell us about these little things, you know.

I don't under stand what I left out? I need a timed relay that uses power as a switch not a push button or toggle.

Thanks, can you show me where they need to be connected. I have extra diodes and caps. Just need to know the values and where.

 

[duffy]

I think you just need a simple transistor circuit. I will draw one up.

Power comes on, relay comes on, 15 seconds later relay shuts off and stays off till the power is cycled again, right?

 

[zone97]

For what you are trying to do, a 555 is more trouble than it's worth. You need one crummy transistor with a cap and a diode and a couple of resistors on the base.

Hey im all for simple. Would you be so kind as to hook me up with a diagram?

Thanks.

 

[zone97]

I think you just need a simple transistor circuit. I will draw one up.

Power comes on, relay comes on, 15 seconds later relay shuts off and stays off till the power is cycled again, right?

That would be wonderfull. Thanks.

 

[duffy]

Here you go. Not super accurate, but will save you headaches over trying to get the 555 to do this one very simple thing.

 

[zone97]

Here you go. Not super accurate, but will save you headaches over trying to get the 555 to do this one very simple thing.

Thank you, BTW what program did you use to create the diagram in?

 

[duffy]

That was Orcad.

 

[duffy]

BTW - how are you turning this circuit "off"?

If you have something like a 12V wall-wart in an appliance timer, you may need to add a resistor across the power supply or NONE of these circuits will work.

 

[zone97]

BTW - how are you turning this circuit "off"?

If you have something like a 12V wall-wart in an appliance timer, you may need to add a resistor across the power supply or NONE of these circuits will work.

I have a digital wall timer, that is programmable down to the minute, but for my application 60 seconds is too long of a time to be on. (It is for a misting system for a vivarium) So I needed something to cut that time down to anywhere between 5 - 30 seconds.

What resistance value would you suggest.

 

[duffy]

1k, 1/4w. Without it, the voltage may never really go all the way to ground.

 

[zone97]

1k, 1/4w. Without it, the voltage may never really go all the way to ground.

Thanks. Now believe it or not, I once held a degree in electronics. But that was like 15 years ago. I dug out an old program I had to make circuits. I traced out the original device I posted a photo of. But could not get it to work. I also tried your new schematic and couldn't get it to work either. Dunno maybe I wasn't doing something incorrectly. Here is the Tm15 if anyone wants to look at it. I also download a trial of the old workbench tool, its called multisim now. Coudln't get it to work with these circuits.

I tried it this way, as having all these failed projects is getting pricey.

 

[duffy]

I built the circuit I showed you and it works fine.

 

[zone97]

I built the circuit I showed you and it works fine.

Can you export your project, so i can try it in multi sim, maybe I did something wrong?

 

[duffy]

Build the circuit and try it with Multimeter.

 

[zone97]

Build the circuit and try it with Multimeter.

I did, couldn't get it... Here is my project. in netlist format.

 

[duffy]

Need more than "couldn't get it" to help you. And I mean actually build it with wires and all, not on a simulator.

The collector of the final transistor should start at 0V, stay there several seconds, then go up to 12V. The base of the first transistor should be at 1.4V, stay there several seconds, then drop to zero. What are you getting?

 

[zone97]

Need more than "couldn't get it" to help you. And I mean actually build it with wires and all, not on a simulator.

The collector of the final transistor should start at 0V, stay there several seconds, then go up to 12V. The base of the first transistor should be at 1.4V, stay there several seconds, then drop to zero. What are you getting?

Oh, sorry. I meant that from my previous posts, that all these "physical" builds are failing and its getting expensive to "test" so I went digital so I can see it doing what I want before I invest in building another physical device. Now I bought all the parts from your diagram with some exchanges. Here are the parts I have.

Instead of a 1n2222, I have ecg123a
Instead of 1n4004, I have a sk3017b

all the other components are as given. Sorry If I was vague earlier. Just pulling my hair out for something that should be so simple.

BTW, I did assembly it on a protoboard and it didn't do anything. The relay never tripped. (my multimeter's batteries died so i couldn't take readings.)

 

[duffy]

Get batteries for the multimeter. You are flying blind without it. Could be the power supply is dead, or something's hooked up backwards, or anything.