PID/SSR alternative

[Snappy]

I have brew kettle with 2 kW heating element. After achieving desired temperature I need to reduce power of heating element.

I suppose that is possible manually with SCR voltage regulator like this one:
http://www.ebay.com/itm/2000W-220V-AC-SCR-Electric-Voltage-Regulator-Motor-Speed-Control-Controller-/331071115259?pt=LH_DefaultDomain_0&hash=item4d15604ffb


Next idea is that in future I replace potentiometer with optocoupler, maybe something like this: 4N35 optocoupler http://www.ebay.com/itm/4N35-10-pcs-Phototransistor-Optocoupler-Optoisolator-30V-60mA-100mA-max-USA-/181637331541?pt=LH_DefaultDomain_0&hash=item2a4a6dba55


Inputs for optcoupler would be controlled via Arduino, and hopefully I can make 0-5V pwm exit from Arduino to drive optocoupler, and change resistance in place of removed potentiometer? Is this good idea?


Is there any other component which can regulate 220V AC power for heating element?

I have found some proportional SSR's but they are quite more expensive, and they need more space and demand cooling which is hard to fit into my existing box. Any other idea?

 

[BigBlock]

I have an omega pcm-1 that I grabbed off of ebay. I think the latest versions are pcm4 or pcm5. The unit attaches to the ssr and takes a 4-20ma input. It outputs a time proportional signal and is used on zero cross ssr's. the switching rate is relatively slow but fine for brewing. I was able to grab an SSR / PCM 1/ heatsink off of ebay for under 40.
The 4-20 input isn't ideal for an Arduino but it's still doable. I used a click plc from automation direct to drive mine as well as execute my full automation control code.

 

[doug293cz]

I have brew kettle with 2 kW heating element. After achieving desired temperature I need to reduce power of heating element.

I suppose that is possible manually with SCR voltage regulator like this one:
http://www.ebay.com/itm/2000W-220V-AC-SCR-Electric-Voltage-Regulator-Motor-Speed-Control-Controller-/331071115259?pt=LH_DefaultDomain_0&hash=item4d15604ffb


Next idea is that in future I replace potentiometer with optocoupler, maybe something like this: 4N35 optocoupler http://www.ebay.com/itm/4N35-10-pcs-Phototransistor-Optocoupler-Optoisolator-30V-60mA-100mA-max-USA-/181637331541?pt=LH_DefaultDomain_0&hash=item2a4a6dba55


Inputs for optcoupler would be controlled via Arduino, and hopefully I can make 0-5V pwm exit from Arduino to drive optocoupler, and change resistance in place of removed potentiometer? Is this good idea?


Is there any other component which can regulate 220V AC power for heating element?

I have found some proportional SSR's but they are quite more expensive, and they need more space and demand cooling which is hard to fit into my existing box. Any other idea?

First, make sure you have GFCI protection on your power going to your element controller. Your a$$ should be worth more (at least to you) than any money you save by not having GFCI.

Second, start reading in the electric brewing forum, rather than the automated brewing forum. A good place to begin is: https://www.homebrewtalk.com/f170/electrical-primer-brewers-145019/

Most SSR's are optically coupled so that the logic inputs are dielectrically isolated from the high voltage/current triac. No need to add your own optoisolator between your logic controller and SSR.

The cooling required will be about the same for any solid state device capable of switching the same load current. You are probably deceiving yourself about the cooling requirements of the linked controller.

 

[Snappy]

@BigBlock: tnx for idea, but still looking other solutions

@doug293cz: don't worry about me getting electrocuted, I know enough about electricity, but electronics is new topic for me, and I do not know all options I have for some single problems ..

My SCR voltage regulator from link above has B500K potentiometer and I need to replace it with some element which I can drive from Arduinos 0-5V pin. I'm not sure if this even exists, searching for options .. or alternative ..


Btw. I tried today my SCR with 2kW heating element, and it's getting quite hot also .. I have to consider that ..


Anyhow, I'm moving this to Electric Brewing forum ..

 

[alphaomega]

I'd suggest you don't use an SCR or SSVR. It is just not the right tool. There is no need to use phase angle control to power control the heater. It will produce unneccesary electrical/electromagnetical noise.
Use a zero-crossing SSR. It can connect directly to the Arduino and is a lot safer, simpler, cheaper and all around better solution. Just control power by feeding the SSR PWM in the 1Hz range or slower.

 

[Snappy]

@alphaomega: yes, I am on that path.

I have implemented PID library to control timings, that part works ok. At first during test it was connected to mechanical relay, and that works fine.

Yesterday I replaced mechanical relay wit SSR, but it seams that Arduino output from digital pin is not strong enough (?) to drive it directly. LED on SSR turns on/off as it should, but 220V output sometimes fires up, and sometimes not. Delay shold not be problem because I have range from 0 to 2000 ms.

I tried to drive SSR input from Arduino pin by putting NPN transistor in between (I have BD241, TIP29C and BD243C on hand) but also similar thing. SSR thus not fire every time. Unfortunately I don't have another one to test is it fault within SSR.

But, when do not use arduino pins, and instead I connect SSR input to + and - 5V supply directly, it fires ok every time ...


Arduino is nano type, and SSR is like on attached photos..

What's wrong ?

 

[alphaomega]

Good (that you are on that path, not that you are having issues)!

It is not easy to say exactly what the problem is, especially as I don't have all the info.
If you are sure the SSR functions when you use just +5V as input, then I would also assume it is ok.
The arduino should be able to drive an SSR directly, but if it has an indicator LED, it might put too much load for one pin.
Of course I dont know your sketch either, so it might be an issue there. Make sure your pin is an output. I dont know how you connected the transistor either.

If your pin can't supply enough current, it is easiest to use two pins for output, though you need to take care not to short these pins (either by not using the arduino framework, to set the ouputs simultanously) or add diodes to the outputs to ensure current is not flowing into the pin.