Ssr Issue?

[QldKev]

OK, before I raise it with the ebay supplier my pid/ssr setup is not fully dropping the voltage in the circuit when the SSR is switched off.

The unit is this on http://www.ebay.com.au/itm/220890859067?ss...984.m1497.l2649

It is wired up as per their diagram


When the system is switching power on,
There is 12v DC on the input to the SSR, and the SSR LED lights up.
There is 232v AC on the output terminal (term 2, to a neutral feed)

When the system is switching power off
There is 0v DC on the input side of the SSR, the SSR LED is OFF
There is 100v AC on the output terminal (term 2, to a neutral feed)

Does this mean the SSR is leaking voltage and therefore is stuffed?
(I think the answer is obvious and is yes, but thought I had better ask)


QldKev

 

[matho]

hey kev SSR's leak current when switched off (about 3 - 8mA) what type of load do you have connected?

 

[QldKev]

hey kev SSR's leak current when switched off (about 3 - 8mA) what type of load do you have connected?

Just a stc-1000 with no load on it, so just ~3w. I just was surprised the stc-1000 kept working, so I checked the voltages.

I'll place a bigger load on it, and see how it goes.

QldKev

 

[matho]

Just a stc-1000 with no load on it, so just ~3w. I just was surprised the stc-1000 kept working, so I checked the voltages.

I'll place a bigger load on it, and see how it goes.

QldKev

ahh that makes sense, SSR's switches current and aren't isolation points cause they will always let voltage through, if you connect a 2000w load then the volts should be about 1 - 2 volts cause its letting 3-8mA run through the 28ohm load, the higher resistance the higher the volts.

cheers steve

edit: correction: across a 28ohm load with 3 - 8mA running thru it the voltage should be about 0.1v to 0.2

 

[QldKev]

Just tried the kettle, my digi-meter showed 0v AC, thanks for the help

QldKev

 

[QldKev]

When you do the auto calibrate, should I have it hooked up to my HERMS and a batch of wort running thought it? or can you run auto calibrate with no load and the probe just sitting in the air?

QldKev

 

[matho]

sorry kev never played with a pid unit so I don't know

cheers

 

[raven19]

I would auto calibrate with water or brew a typical batch - it will calibrate pretty quickly if its anything like my el cheapo PID. My auto tune was all done within 10mins iirc, then it ran as per normal during the mash. Beer turned out fine!

 

[QldKev]

sorry kev never played with a pid unit so I don't know

cheers

OK, thanks for the help on getting it verified. I find my internal RIMS doesn't overshoot by much (not much a thermal mass) but the HERMS can jump around a bit, so though this may be a better solution to help smoothen it out.

I would auto calibrate with water or brew a typical batch - it will calibrate pretty quickly if its anything like my el cheapo PID. My auto tune was all done within 10mins iirc, then it ran as per normal during the mash. Beer turned out fine!

Did you do this during a ramp, or just got it to mash temp then hit the auto calibrate?


QldKev

 

[Wolfy]

Did you do this during a ramp, or just got it to mash temp then hit the auto calibrate?

From the manual (The Auber one that is functionally equivalent to yours):
"During auto tuning, the instrument executes on-off control. After 2-3 times on-off action, the microprocessor in the instrument will analyze the period, amplitude,
waveform of the oscillation generated by the on-off control, and calculate the optimal control parameter value. The instrument begins to perform accurate artificial intelligence control after auto tuning is finished."

Hence, you'd be best doing the auto-tune at the start of your mash process (when you are below your target temp), because once it's reached the correct mash temp the calibration process might push the temperature over your limits which would not be good.

 

[QldKev]

From the manual (The Auber one that is functionally equivalent to yours):
"During auto tuning, the instrument executes on-off control. After 2-3 times on-off action, the microprocessor in the instrument will analyze the period, amplitude,
waveform of the oscillation generated by the on-off control, and calculate the optimal control parameter value. The instrument begins to perform accurate artificial intelligence control after auto tuning is finished."

Hence, you'd be best doing the auto-tune at the start of your mash process (when you are below your target temp), because once it's reached the correct mash temp the calibration process might push the temperature over your limits which would not be good.

Sounds good. I may mash in for a prot rest and then hit the auto tune. Once it's finished playing, then I can just hit in the next step.

Thanks

QldKev

 

[MaltyHops]

I would auto calibrate with water or brew a typical batch - ...

I'd calibrate with water - the point of the calibrating is for the PID
to discover the response of your system so it knows how much
heat to apply and for how long to achieve a set temperature, best
to just let it do its thing once off and then you can play with it.

Is the PID controlled heat the only heat source in your system?
Ie. there's no other separate heating that could interfere with the
PID's control?

 

[QldKev]

I'd calibrate with water - the point of the calibrating is for the PID
to discover the response of your system so it knows how much
heat to apply and for how long to achieve a set temperature, best
to just let it do its thing once off and then you can play with it.

Is the PID controlled heat the only heat source in your system?
Ie. there's no other separate heating that could interfere with the
PID's control?

Funny thing was last night I was thinking about how I will work it as I do have another heat source in the system, the internal RIMS, which has it's own controller.

A typical brew day goes like this

Mash in for 65c
Fire up the pump for recirc
Turn on the HERMS controller for 65c
Leave off the RIMS controller (cause issues with the RIMS and **** getting stuck to element at this temp)
Recirc for 5 mins.

Then set the HERMS to the next step and start ramping
Also set the RIMS to the next 'step - 2c' and start help ramping. ( -2 is because the RIMS and HERMS are in series, and this helps prevent the HERMS being 2nd in line overshooting)
After 5 mins set the RIMS to 'step - 1' (help ensure the bottom of the mash bed is closer to the set point)

Repeat the last stepping procedure for each further step until mashout.



So now I'm thinking if I do the dummy run using water only (say 70L of water to emulate 60L plus grain) to run the auto cal, I could manually switch in the RIMS element whenever I see the PID switch on it's output, that way it sees both elements heat output. Only issue here is once the temp gets close to the set temp normally I have the RIMS set lower, but this could allow me to set both controllers to the correct temp and the PID would be smart enough to cut out earlier.

OR I could throw in a second SSR in parallel to the first one, and control the RIMS from the same PID. Then I could just isolate the RIMS during the first 5 mins.

QldKev

 

[hockadays]

OR I could throw in a second SSR in parallel to the first one, and control the RIMS from the same PID. Then I could just isolate the RIMS during the first 5 mins.

thats what I would do much simplier...