Power supply for solid state relay

[A6INTRUDER]

I am not much on electronics so I was hoping maybe someone here could help me out.

I am redoing my vacuum bagging set up. I bought some vacuum switches off ebay and they are only rated for 1 amp. My motor is 2.1 amps.

So I am going to run a low voltage set up with an SSR to switch the AC to the motor.

I bought an SSR and had hoped to use a wall wart for the low voltage side.
I tried several wall warts and none will make the AC flow. The LED on the
SSR comes on but the AC doesnt flow. So I tried my vairable DC power supply and it works fine with it. I can turn on the AC side with anywhere from 3.5v and up.

The SSR says it can use 5 to 24 VDC to run the low voltage side, I have tried wall warts of 6v 1 amp, 9.6v 50 ma and 12v 100ma (all are dc output) but no joy.

So Two Questions.

1. Why wont a wall wart run the SSR?

Is it that wall warts dont produce clean enough DC to make it work?

2. Where can I get an inexpensive and small power supply in the 5 to 24 v range that would run the SSR?


thanks for any advice.

TIM

[daytriper]

I am not much on electronics so I was hoping maybe someone here could help me out.

I am redoing my vacuum bagging set up. I bought some vacuum switches off ebay and they are only rated for 1 amp. My motor is 2.1 amps.

So I am going to run a low voltage set up with an SSR to switch the AC to the motor.

I bought an SSR and had hoped to use a wall wart for the low voltage side.
I tried several wall warts and none will make the AC flow. The LED on the
SSR comes on but the AC doesnt flow. So I tried my vairable DC power supply and it works fine with it. I can turn on the AC side with anywhere from 3.5v and up.

The SSR says it can use 5 to 24 VDC to run the low voltage side, I have tried wall warts of 6v 1 amp, 9.6v 50 ma and 12v 100ma (all are dc output) but no joy.

So Two Questions.

1. Why wont a wall wart run the SSR?

Is it that wall warts dont produce clean enough DC to make it work?

2. Where can I get an inexpensive and small power supply in the 5 to 24 v range that would run the SSR?


thanks for any advice.

TIM




Tim, Most any of the "wall warts" you mentioned should operate the SSR, just make sure you have the polarity correct and that it is DC voltage not AC. The SSR requires very little power to operate, on the order of 10 to 50 mA depending on the model so you dont need an expensive high current powersupply. Also check the AC side of the SSR for specific marking as to AC Supply or Line, and the other terminal to be the LOAD or output terminal. I have seen some that will not work if not connected properly. You did not say what brand or model SSR you are trying to use or I would have looked it up and could be more help to you.
Heres a link to Omega where you can find a lot of info on SSR's, and very good explainations of the different types.
http://www.omega.com/temperature/Z/pdf/z124-127.pdf
Hope some of my reply was helpful to you.

[A6INTRUDER]

Daytriper,
Thanks for the web site and the advice, that site explains alot.

I did finally get it to work with a Wall Wart, I found one that said Class 2 9.0 vdc and 1000 mah. It made the motor run just fine.
I went back and tried the others and chaged leads around but still no joy with them.
I still would love to know why some will work and others dont.

thanks again for the help

take care

TIM

[jeffs555]

Perhaps they need a filtered DC voltage. Not all of the DC wall warts have a filter capacitor built in. You might try putting an electrolytic cap on the output of one that doesn't work to see if it changes anything.

[A6INTRUDER]

I will give that a try.
I reallly want to know why the others dont work, and I suspect it is just like you said.

thanks

TIM

[phil_g]

Perhaps they need a filtered DC voltage. Not all of the DC wall warts have a filter capacitor built in. You might try putting an electrolytic cap on the output of one that doesn't work to see if it changes anything.

Spot on Jeff, SSRs switch at the AC zero voltage crossing point in order to avoid interference from switching at max load. An unsmoothed wall-wart is producing no voltage at that point - it too is on the zero crossing point.
An electrolytic across the output of the wallwart will fix it, value not critical, say 100uF. This ensures that at the AC zero-crossing point there is voltage available on the input to light the LED in the SSR's opto-isolator (which is all your 'input' does - lights an LED - a few mA)

Cheers
Phil

[phil_g]

... I bought some vacuum switches off ebay and they are only rated for 1 amp. My motor is 2.1 amps.
TBH I'd run through the switches. 2A through a 1A switch is unlikely to do any harm, and its not like its a critical process running continuously is it...
Keep It Simple ! :)
Phil

[A6INTRUDER]

thanks Phil,

Your knowlege is very helpful.

No its not a continuous process, if the bags dont have many holes in them, the pump comes on for maybe 10 second every half hour or so.

I thought alot about running it through the 1 amp switch contacts but wasnt sure weather that would burn them out too quick or not.

I may give that try, but I sure would hate to have them fail when I had a couple sets of wings in the bag. But I suppose that could happen with the wall wart/relay set up too huh????

thanks for the answers.

TIM