Sophos9 - Diy "poor Mans" Reef Cooling

[idlefingers]

Well, new unit does exactly the same thing I've tried using a long extension lead to plug it into a bunch of sockets around the house with no effect so I guess it's just not going to be. The bloke at monitors-direct was a bit vague about what could be wrong with our electrics so I'm not sure whether it's that or there's something wrong with the unit.. saying that, getting a replacement rules that out. I guess it's no temp controller for me..

 

[sophos9]

How strange!?!

Do you have UPS for computers you can get your hands on, that may help eliminate problems?

 

[idlefingers]

How strange!?!

Do you have UPS for computers you can get your hands on, that may help eliminate problems?

Nope, haven't got one of those (or know of anybody with one to test it)

 

[sophos9]

Idle.... you will not believe this!! Mine has started doing what you have been explaining (although its about 0.6dC)

ANDY, where are you?

 

[idlefingers]

How strange! So if it's developed with yours since you've had it hooked up, surely it's a fault with the unit and not the electricity? I wonder if the replacment he sent to me is just one with the same issue..

 

[sophos9]

Dunno, I'm 100% it was not happening - I had heard a few reports of this and totally tested it. Will have another look and play around tonight, bummer!

 

[Underwurlde]

Sophos - take one the the capacitors you have and put it across the input terminals for the temperature sensor. Use the 100nF ones and then the 10nF ones.

Does that make ANY difference?

Andy

 

[sophos9]

Ahhh... Good man Andy, always on the ball!

Will do that tonight and measure the difference!!!

 

[sophos9]

Right, Andy seems to be on the case!

I put a 10Nf Capacitor over the terminals and the temperature read out changed from 26.6 to 27.4C. I checked the temperature with a TMC precision thermometer and guess what... Yep, the actual temperature is 27.5C

Turning the T5's on and off made no difference to the output. Andy, what happened here?

 

[Underwurlde]

noise noise noise.....

what would we do without noise.....

OK....

Capacitors have a 'reactance' or a resistance based on the frequency of voltage applied. Under DC conditions, the capacitor (without getting complicated) looks like an open circuit - looks like there is nothing there. So, in other words, the low frequency DC component of the signal coming down the temperature sensor wire is not effected by it (again, without getting too complicated).

Now, when you up the frequency, the capacitor starts behaving like a resistor (believe it or not), that is to say will convert electrical energy to heat. So, the higher frequency noise 'energy' that I think is effecting the temperature probe / probe wires, is now going into the capacitor and being dissipated as heat (killed off) instead of going into the unit and confusing the AtoD's at the microprocessor inside.

You can think of this as a low pass filter. This should be in the bloody design of the thing and looks like this simple filter trick is missing..... I could be wrong of course, do some more testing see if it really does work long term.

Better still is to use a series resistor (about 4K7) and then couple this to gnd using the 10nF.

Andy

 

[sophos9]

Excellent, I've tested and it seems totally sorted, reading the correct temperature and everything!

All I have done is soldered a 10Nf capacitor to 2 x bits of wire, and secured these using the same screws as the sensor screws....

Check out the pic, dead easy fix!

 

[Underwurlde]

You've been practicing!

Anyway, good job there!

For the record for anyone else wanting to do this, mount the capacitor as close as possible to the input terminals... ideally this cap should be right next to the processor pin on the PCB inside the unit (this not being so in this case probalbly accounts for the 0.1 deg C descrepency).



Andy

 

[sophos9]

Good teacher

Idle will be well happy!!

0.1dC I can deal with, the fans are going crazy now trying to bring the tank temperature down, luckily evaporative cooling takes a while and the additional 110w of T5's are burning until 30mins before close of photoperiod!

Andy, thanks again mate - you're a credit to this forum

 

[idlefingers]

Nice job!!

Sophos, would you be willing to build another and send it my way if I send you a few squid to cover the expenses (and your time)?

I think it's pretty pants that they haven't built something like this into it to begin with.. especially if they're aware of the problem!

 

[sophos9]

Sophos, would you be willing to build another and send it my way if I send you a few squid to cover the expenses (and your time)?

Hi mate, no problem will do it for nowt... Will be glad to hear that its all working for ya!