PTS Flowbench Forum

FWIW, I've got a couple of ideas for a computer interfaced PID depression controller, for use with a random turn-on SSR. I've got a lot on my plate right now so I'm not sure when I'll get around to putting something together but when I do, I'll let you all know.

Hey Bruce I am glad you arrived,I am going to buy this given that is has already heat sink,SSR and Pulse Control module.The transformer will be the most inexpensive part seeing that the control module would use just 20 aMdc and I will test with one motor seeing that the SSR is just 10 amps.I also have a electronics tech with over 30+ years in electronics at my office so we will both work together and figure this out and let you all know how it works out,thanks again and all inputs they are always welcome.
http://www.ebay.com/itm/Omega-SSRL240DC ... 231d61cdf2

watercooler wrote:
Hmmmmmmm, so Tony don't that unit uses pulse to control voltage? I just think that I could buy or make a circuit that could operate the same, I am still doing some research and came across this Pulse Control Module thats design for SSR take a look

http://www.ebay.com/itm/Omega-SSR-Serie ... 23245d1da9
and here is the datasheet on it,its 2 to 20 mAdc ranging from 0% to 100% I would just need a driver to drive it?
http://www.omega.com/manuals/manualpdf/M0957.pdf
Sorry for being so hard headed but I just think there is a cheaper solution than spending a bunch on a controller and do they sell it separate from their SSR? I will check again and see if they do and thanks to you and everyone input its very valuable.

What that particular Omega module does is switch the load fully on and then fully off once each second.
Ten percent power is on for 0.1 seconds, off for 0.9 seconds.
Seventy percent power is on for 0.7 seconds off for 0.3 seconds.
Ninety four percent power is on for 0.94 seconds off for 0.06 seconds.
It is strictly for controlling an electric heating element, it has no other practical use.

The PID temperature controller you found earlier does the same thing, switches a load either fully on or fully off.
Usually the cycle time is adjustable via the key pad, typically from 1 second to 99 seconds in one second steps.
These are often used with gas burners that cycle on and off maybe once each minute, or electric heating elements that cycle fully on and fully off repetitively with a varying on/off duty cycle.
These controllers are capable of very precise proportional temperature control, but definitely won't work with a motor or lamp load, the slow pulsing would be really objectionable..

What is needed to drive your SCR random fire power module adjusts the proportional on and off time, every half mains cycle, phase and frequency locked to the 50Hz/60Hz mains frequency.
The HB Controls controller switches on and off at 100Hz or 120Hz synchronised to the mains.
That is fast enough that the vacuum motors see it as continuous power.

Another class of controllers altogether are the high frequency PWM motor controllers, for dc motors.
These usually switch at very high frequencies, not synchronised to the mains frequency, and also useless for what we are trying to do.

The HB Controls controller is rather special, it does exactly what we want, and I believe they will sell just the circuit board by itself as a spare replacement part, for less than buying it all complete with the SCR power module and heatsink.

Thanks for your input Tony I totally understand whats going on now and the difference between both.I will go ahead and purchase the CRYDOM RELAY CWD24125-10 & ECD PHASE ANGLE CONTROLLER and carry it to work and ask the tech to take a look and see if we can make it work by some modification and adding a POT.

I cannot find any data or specifications for the ECD control board, but if it is supplied together with the random fire SCR module by Crydom, I think you can be pretty sure it is the right thing.

Great! thats what I was hoping to hear I am ordering it now and once we figure out the schematic we can then make it work the way I want it to.I will update everyone once progress is made.

Looking at the pics there seems to be jumpers and pins so I would assume you can make the phase angle control work off various inputs one being a pot control. It has a 3 pin terminal block on one side where the pot would attach and the other side 2 pin terminal would be the transformer power.

The hardest thing to find for these setups are the large heat sink, they stopped making the "HE" model and I had a heck of a time to find a supply of heat sinks for my setups.

Just a flat rectangular aluminium plate 1/8 thick, with the SSR bolted right at the middle would make an excellent heat sink, cheaper too.

If mounted vertical on spacers so air could convect both sides, a rough guess might be about two square inches of surface area per amp minimum.

Hey guys I found some for cheap check them out.The HE model seems to be discontinued and the HS is the current model and a few more.
http://www.ebay.com/itm/SSR-Heat-Sink-2 ... 231dc02461
or
http://www.newark.com/crydom/hs072/rela ... dp/50R4613

Brucepts wrote:Looking at the pics there seems to be jumpers and pins so I would assume you can make the phase angle control work off various inputs one being a pot control. It has a 3 pin terminal block on one side where the pot would attach and the other side 2 pin terminal would be the transformer power.

Exactly my thoughts Bruce,I bought it today and it was even cheaper when I choose USPS priority shipping $10 over their default UPS shipping $17.I cant wait to see whats in store and much thanks Tony and everyone for the help,if not I would still be searching forums and datasheets haha.