Tricky wiring thread

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Njguy

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This is a confusing one

Basically I am using two solid state relays switched by two inductive proximity sensors to each turn on a pair of inductors.

My inductive proximity sensors work with the relay in that it trips it no problem. My problem is that when my relays are connected to their loads, the whole system flickers. When I say flicker, I mean that both led's on the sensor and relay flicker which means my relays are switching off and on...which is bad. Under no load the sensor and relay is steady. I'm thinking that it has do with the fact that everything is connected to the same power supply, in fact I know it is because if I use 9 volt battery and connect it to the load end of the relay, it is steady as it is a separate power supply. Any help?? Please ask for further detail if its confusing.

PWM = Pulse width modulator.
IPS = inductive proximity sensor

IPS1->Relay1->2 inductors
IPS2->Relay2->2inductors

My power supply is a 12 volt adapter that plugs into the wall

My relay is Relays - Solid State - SSRDC100V40A

My IPS is AIS18F08AP024-Q65, PROX, 18MM, PNP, NO, 8MM RG, QD (M12 3 WIRE), Proximity Sensors - automation products from Automation 4 Less
 

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MORE details please.

You say you are connecting a 9 volt battery to the output of the relay, but is this including the load or are you just checking to see if the voltage passes through the relay with a meter?

What are the values of your power supply, is it a battery? Calculate the power usage of your circuit and the ability of the supply. Get a new one if you must.

Or perhaps the SSRs do not like pulsed DC. I know AC SSRs will not pass DC of course.
 

The 9 volt was a test. It was to see what would happen if the load end of the relay was not connected to circuit power supply. And the the relay is steady because of it.

My power supply as I said is a 12 volt dc adapter that plugs into a wall. This is a Dc ssr as the link says.
 

The relay was steady, but were you powering the load or just connecting the battery to the SSR and checking voltage with a meter? This is what I was asking.

A wal wart? What is the POWER DRAW of your circuits? these are inductive loads so I think its a safe bet that it is no in the milliwatts. What is your power supply rated for? 12 V, 500 mA? Now, what are all the components in your circuit rated for as a total load? If you are exceedling the power supply, get another one rated higher. Give yourself 10-20% more than you need at LEAST.

I understand that it is a DC SSR, but it appears that you are pulsing your circuit. I do not know the frequency or whatever, but knowing what I know about AC SSRs, you might be having trouble with the DC because of the pulsed load. Your 9 volt battery, I assume, was giving it a steady voltage no? This is just a thought, BTW. I tend to think you are loading the power supply too harshly and just need to get another one.
 
OK, JUDGING by the drawing, you have the same load and everything when you do your 9 volt thing.

Get another power supply.
 
Well, if you are driving the coils with PWM and switched through a SSR with no snubbers on the coils, then yea, it's going to be a problem. The inductive kickback of the coil is getting into the IPS and causing random behavior. You need snubbers on the coils to keep the inductive kickback of the coils out of the power supply leads.
 
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Its not the coils if you look in the simplified image, there is no coil, just a basic load. It still spazes out. Its gotta be some sort of basic wiring that I'm overlooking.
 
Njguy said:
I need it to be the same power supply that's the point
Click to expand...

I didn't say, "add another power supply", I said, "get another power supply. If your overloading it, it is too small and needs to be replaced with something more suitable.

It doesn't make sense why its doing this, it is a parallel circuit.
Click to expand...
Huh? What does that have to do with anything? Each parallel branch you add to a circuit will load it further. I would say that paralleling is typically how circuits get overloaded, adding more series resistance reduces the loading effect. You have parallel/series backwards in that regard.

Also, the advice about snubbers is valid from the other poster, but you shouldn't be guessing about this. You need to calculate your load impedance and comparing the draw to the abilities of your walwart. I wouldn't expect the typical 500 mA walwart to power too many inductive loads without trouble, especially in parallel at the same time.
 
if you have a oscilloscope you can simply see wheather the supply has any problem or not, if the terminal voltage is having big flaxuation you may face this problem. or the power supply may momentorily stop and start due to over load. no other chances i think.
 
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I realize the use of snubbers. I didn't include it here as it's too much information. My power supply is 2 amps @ 12 volts. More than enough I'm sure. And again you seems to be missing the part where i took out the loads and it still does it when connected to the same supply.
 
What type of resistive loads are you using? Are they wirewound resistors? What resistance are they? Maybe post a photo of your setup. What happens if you do this:
 

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I thought you said you did your experiment with a 9 volt battery and it stopped?

You took out the loads and replaced them with what?
What are the specifications on your load components? How many of them are there? I see four plus your PWM circuit and the sensors. "More than enough I'm sure", Have you actually done the math to figure that out?

Are they motors? Solenoids? Are they physically loaded, doing work? A modest DC motor can easily approach an amp of current, especially if it is under a load. Four of them in parallel and you may be taxing your power supply, especially with other circuits involved.

What did you replace the loads with in your test? A resistor? What was its value?

I'm trying to help here. You haven't been providing values, only pictures. They don't tell the whole story.
 
ke5frf said:
looking closely at these drawings, I hope you don't have the supply shorted when you close your switch.
Click to expand...

Ill look into you drawing but I think it was just a drawing mistake I made with the short.

I narrowed down the problem to the relay. It seems that if both ends of the relay are connected to the same power source, the relay doesn't function. The load in the picture just represents the load end of the relay.

This drawing is supposed to be a parallel circuit with some power keeping the relay on, which turns on the load of the relay. But it doesn't every thing goes dead.
 

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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.
 
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.
 
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