voltage drop in SSR

[wuttheheeck]

long story shot I am adding a float switch to my pump control for auto sparging. I have already wired up elements through ssr's but im having trouble now.

I am experiencing a voltage drop over the ssr, Volt meter reads 117 volts on the input to SSR and reads 23 on the output of the power side. I was using my neutral bar for the black probe.

Im controlling the switching side with a 5v, and some small current, but the SSR led is illuminated.

Any possible causes or did i just buy a bad one off the chEapbay

 

[andrhamm]

i have the same problem with two that i bought on ebay so im thinking im doing something wrong. subscribed.


Sent from my iPhone using Home Brew

 

[Brumateur]

Could you provide a link(s) to your SSR supplier?

 

[IslandLizard]

Is 5V enough to open the gate fully? Aren't they more in the 12-24V range?

 

[Brumateur]

Most of SSR rated 3-24V for control input. I did use 5v without a problem.

 

[muhteeus]

What is the voltage drop/ohm reading across the SSR output terminals? Which leg of the element are you switching?


Can you post a pic of the wiring on the ssr?

 

[wuttheheeck]

Here is the exact one I bought. I was wondering if the gate would only be partially opened. Maybe ill run a larger voltage through just to test.
http://www.ebay.com/itm/221336169985?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

 

[sandyeggoxj]

Is your signal voltage actually 5v at the relay? Does it have enough current to fire the relay? How are you measuring your voltage post relay?

 

[atoughram]

Even my "Expensive" Auber SSR's leak a small amount of current. A couple of questions.

1) is there a command on the SSR to flow current?? (5 volts present on the input side)

2) If there is no command, do you have the element still connected in the circuit?

If 5V command is not present and the main load (element) is not present in the circuit, you will get some leakage voltage.

I've got a couple of Crydom SSR's laying around - good old made in North America stuff - and I bet they leak too.

 

[atoughram]

Here is the exact one I bought. I was wondering if the gate would only be partially opened. Maybe ill run a larger voltage through just to test.
http://www.ebay.com/itm/221336169985?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

I've used those with 5V before without problems.

 

[ajdelange]

SSR's do leak and they do, when turned on, have voltage drops across them but not as much as (117 - 23). A couple of volts measured between the load side terminals with the the thing under load is more like it. TTL levels (5 V) are commonly used to control them so that should be plenty. You may have a bad SSR. They do fail.

 

[wuttheheeck]

I measured 5v at the control end of the SSR. I then tried using a 12v supply as the switch for SSR and found that the LED was brighter and than I had 75v at my pump outlet.

This is a large improvement, and makes me want to belive that a large switching voltage closes the circuit even more.

Since I am running the switching connection through the mashtun and it will be partially submersed in the mash I dont want a large voltage (for obvious reasons) but I still need to get ~110 to my pump power.

Is your signal voltage actually 5v at the relay? Does it have enough current to fire the relay? How are you measuring your voltage post relay?

 

[sandyeggoxj]

You are still looking at a >30% voltage drop across the relay. That isn't acceptable. Do you have a picture of your control panel with the relay?

 

[wuttheheeck]

You are still looking at a >30% voltage drop across the relay. That isn't acceptable. Do you have a picture of your control panel with the relay?

Not the best artist, but here is the enclosure, hope my denotions help.

Thought i might as well include the front of the box and float switch. My first images on HBT of my herms setup

 

[Brumateur]

Connect any load to your pump outlet. Incandescent lamp for example. Triac inside an SSR needs to have some current flow to be opened fully.

 

[ajdelange]

This is a large improvement, and makes me want to belive that a large switching voltage closes the circuit even more.

It isn't really. An SSR is a switch, not an amplifier. It is designed to be either full on or full off. If its impedance depends on the level of the gate signal it isn't functioning properly.

 

[wuttheheeck]

Is there a minimum switching current for SSRs?

 

[wuttheheeck]

Connect any load to your pump outlet. Incandescent lamp for example. Triac inside an SSR needs to have some current flow to be opened fully.

Connected to lamp, lightbulb flashes periodically. Using a floressent bulb, not sure if that helps either. Like I said before was only reading 23v from the pump outlet.

I know theres some power, but not the full `120v.

 

[Brumateur]

Connected to lamp, lightbulb flashes periodically. Using a floressent bulb, not sure if that helps either. Like I said before was only reading 23v from the pump outlet.

I know theres some power, but not the full `120v.

Connect a pump and see if it will work.

 

[atoughram]

I measured 5v at the control end of the SSR. I then tried using a 12v supply as the switch for SSR and found that the LED was brighter and than I had 75v at my pump outlet.

This is a large improvement, and makes me want to belive that a large switching voltage closes the circuit even more.

Since I am running the switching connection through the mashtun and it will be partially submersed in the mash I dont want a large voltage (for obvious reasons) but I still need to get ~110 to my pump power.

Is this with a load, such as a 60W light bulb or a chugger pump in the circuit?

 

[ajdelange]

Is there a minimum switching current for SSRs?

There is a 'holding current' i.e. a minimum required to keep the device conducting but as the gate is being applied continuously that shouldn't be an issue.

 

[wuttheheeck]

I use a two pump system, and this one being controlled is a 12vdc pump used for HLT circulation and sparge only. Instead of switching the ssr with 5v I bumped it up to 12v 750mA and it is enough to power the pump.

thanks for the help everyone

 

[ajdelange]

None of that makes sense. If you try to control a DC load with an SSR it will never commutate and keep conducting even if you remove the gate signal. The gate signal should have no effect on the output (other than switching it on an off) as all it does is light a LED. The led shines on photosensitive device connected to the triac or SCR's thus isolating the control circuit from the AC circuit.

The only thing I can thing of here is that somehow the gate signal is getting to the motor and that doesn't make a lot of sense either.

 

[atoughram]

So... Your controlling a DC pump with an AC SSR???

Well there's your problem right there....

 

[sandyeggoxj]

I'm glad we are all confused here. Ha!