Tricky wiring thread

[Njguy]

That just can't be. SSRs are optically isolated, the load end shouldn't give a hoot where its power is coming from.

Really man, I don't want to be off on a tangent here without all the information. I'm trying to be helpful. I am not assuming that you don't have the proper equipment, or that you don't have this all figured out, but it would help to know specific values on your resistive loads, your inductive loads, your PWM and sensors, etc. If you told me you were using a 100 K resistor and it still flickers, I'd forget about the whole power supply thing. Otherwise I can't help but wonder about your supply.

I used many different things. A few Led's, a tester, a roughly 1 amp inductor etc.

I'm telling you if both ends of the relay are connected to the same battery the led on the relay goes off. If you take away one wire on the load end it goes back on. Driving me nuts cause it makes no sense.

 

[Njguy]

Also, this just occured to me. DC SSRs require a minimum load current to function as well, so "underloading" might be a problem. You may need a parallel resistor with the load if it isn't sufficient.

could you explain that a bit better, parallel resistor

 

[kchriste]

I'm telling you if both ends of the relay are connected to the same battery the led on the relay goes off. If you take away one wire on the load end it goes back on. Driving me nuts cause it makes no sense.

Then your battery is nearly dead or too small for the application.

 

[Njguy]

Then your battery is nearly dead or too small for the application.

Even with no load? Cause it does that with no load at all aswell.

 

[kchriste]

Which is it then? First you say:

If you take away one wire on the load end it goes back on

Do you mean you are connecting the SSR output across the battery without a load? A photo at this point would really help.

 

[Njguy]

Also, this just occured to me. DC SSRs require a minimum load current to function as well, so "underloading" might be a problem. You may need a parallel resistor with the load if it isn't sufficient.

Hey I got it working by following your tip. That was it. Never would have suspected it. Thanks man your a life saver.

 

[mbarazeen]

just post all the values and specification of the supply etc as others requesting then for sure you will get a congrete answer from any one, also make sure your connections are not lose any where, or you use a common wire and split it for both modules.

 

[Njguy]

Alright I will in a bit, but I still working it out, because the resistors only seem to help it when wired in series not parallel, which is kinda bad.

 

[kchriste]

Connect a voltmeter directly across the battery and tell us what the voltage is when it is not working and what the voltage is when it is working.

 

[ke5frf]

Alright I will in a bit, but I still working it out, because the resistors only seem to help it when wired in series not parallel, which is kinda bad.

If the resistor is helping when wired in series, you are definitely overloading the power supply without the resistor. The resistor is reducing the current flow down within supply specifications.

I don't think it could be more obvious.

And your tests with other loads, in those cases you may have been "underloading" the circuit, I can't be sure without knowing the values of the components. Just realize, those are 40 amp SSRs, they are designed to switch fairly heavy loads, not 1 megOhm resistors. It really sounds like your having trouble targeting your overall load current to withing both SSR and power supply specifications.

 

[ke5frf]

I also am not sure about your PWM method. I'm not an expert with those kind of motor control circuits but I do know a little. Wouldn't it be better to PWM the input to the SSR rather than have the SSR switch PWM power at the load terminals? Usually you modulate a switch at the signal side. This relay may not be recovering properly between pulses on the output. Just my take on the design concept here.

 

[Njguy]

I found out what the problem was. I am man enough to admit that the wires were not tightened to the relays enough. They apparently gotta be pretty tight. Problem solved. Now I must hang my head in shame.

Before when it wasn't tight enough, the led flickered with a regular interval.

Ke5frf thank you for your help. It was your suggestions that indirectly led me to the discovery. Thanks a lot!