CNC4PC C5 solid state relay board problem

[llamatrails]

I bought it in October, and never got any response from them at that time with my initial setup questions. Sigh. Got it running for my spindle, and now am having issues with hooking up a shopvac. Again, using their website trouble ticket system, no response from them after 3 days of waiting.

It is setup with emc2 running it, wired through a breakout board.

If I place a low load on the 40A triac, switch 1, emc has no problem turning it on and off. For instance, I have a hanging flex grinder for my spindle, a knockoff of the Foredom units. This turns on and off perfectly.

The issue is with a high load, my 11.5A shopvac plugged into switch 1. It will turn on, and I can turn it off within the first minute or so. If I wait, say 5 minutes, then I cannot turn it off.

Since the low load spindle works, I don't see my wiring or emc as being the issue. All I'm doing is changing the AC plug for the load. The spindle always turns off, while the shopvac won't after a few minutes.

Any ideas ?

[Al_The_Man]

The first thing I would do is lift off the low voltage input terminal while the Vac is running and see if it stops, if it carries on running then for some reason the SSR is latched in.
If it stops, then obviously the problem is in the trigger side signal somewhere.
Al.

[llamatrails]

Al,
Thanks for the assist.

I pulled the signal line to the C5 switch 1, and it keeps on running and running and running ...

I also metered the signal line. When the shopvac is supposed to be off, it reads +.025 vdc and it is +5.12vdc when the shopvac is supposed to be on. emc is doing its' job.

Looks like the SSR gets saturated after a few minutes, and the only way to stop it is to pull the AC plug. Kinda' defeats the purpose ...

If the triac was bad, I'd think that the low load spindle would behave the same way, but it turns on/off as it should.

[Al_The_Man]

I have never come across that before, what is the part number of the SSR?
Al.

[llamatrails]

Originally Posted by Al_The_Man I have never come across that before, what is the part number of the SSR? Al.

The triac is a BTA40.

[Al_The_Man]

Is this a discrete SCR not a opto isolated type SSR?
You would be better off using that type if this is the case.
Al.

[llamatrails]

Originally Posted by Al_The_Man Is this a discrete SCR not a opto isolated type SSR? You would be better off using that type if this is the case. Al.

Here is a link to the SSR relay board, switch 1:
http://www.cnc4pc.com/Tech_Docs/C5R3_WD.pdf

The parallel port lines are buffered on the breakout board, and I am using parallel port pin 17 (top left corner):
http://cnc4pc.com/Tech_Docs/C10R8_WD1.pdf

[RomanLini]

That triac is 700v 40A rated so it should work ok provided it is adequately heatsinked.

If it's not kept cool enough, then after it gets hot you might be getting false triggering. The PCB layout doesn't seem to provide enough room for good heatsinking, in fact it is a poor layout with the heatsink in the middle of the PCB that means you can't easily add a larger sink or sink to chassis etc.

Try blowing a small desktop fan on the sinks while it is running, but be careful with the PCB exposed as this is live mains equipment!! If that fixes it then you know it is an overheat fault and that will open up some options for a solution.

[llamatrails]

Originally Posted by RomanLini That triac is 700v 40A rated so it should work ok provided it is adequately heatsinked. If it's not kept cool enough, then after it gets hot you might be getting false triggering. The PCB layout doesn't seem to provide enough room for good heatsinking, in fact it is a poor layout with the heatsink in the middle of the PCB that means you can't easily add a larger sink or sink to chassis etc. Try blowing a small desktop fan on the sinks while it is running, but be careful with the PCB exposed as this is live mains equipment!! If that fixes it then you know it is an overheat fault and that will open up some options for a solution.

I pulled the board, and the bottom was discolored under the 40A triac. Each of the 4 triacs have a heatsink, but the 40A one is way too small, obviously.

I've lifted the 40A triac up from laying on the board, and put on a bigger heatsink, with thermal grease, which wasn't there. When I tested the shopvac now, the triac temp got up to 200deg F so I shut it off.

Thanks all, I now see the problem, and will work with it. Next step is to put a fan on it, hopefully get the temp down. Maybe a combination of a larger heatsink and the fan will do it.

[RomanLini]

Good, you got it sorted! But that triac might now be damaged from its previous overheating. It takes some nasty temperatures to discolour the PCB.

Now you know more about the situation it is probably good insurance to replace it with a new triac, and I would suggest using a higher rated part if possible, and definitely with much better heatsinking.

Ultimately you are probably best off with Al_The_Man's suggestion to switch the shopvac with a good solid state relay, I would use a 100 amp one on a decent heatsink of its own. An 11 amp mains motor load is not a trivial load.

[llamatrails]

Originally Posted by RomanLini Good, you got it sorted! But that triac might now be damaged from its previous overheating. It takes some nasty temperatures to discolour the PCB. Now you know more about the situation it is probably good insurance to replace it with a new triac, and I would suggest using a higher rated part if possible, and definitely with much better heatsinking. Ultimately you are probably best off with Al_The_Man's suggestion to switch the shopvac with a good solid state relay, I would use a 100 amp one on a decent heatsink of its own. An 11 amp mains motor load is not a trivial load.

I am now seeing the temp stay below 120degF with a fan on it.

Yep, I agree, for safety sake, I'll be checking into a solid state relay instead.

Thanks again, all, for the assist.