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G'day Guy's,
Recently I got a temp controller off fleabay for just under $15 delivered and after a few tweaks got it working on my Canadian blonde brew. http://www.ebay.com.au/itm/280949513312?var=580128825374&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 that is the controller and as it switch's on when the temp rises one needs to invert the switching so it will switch on dropping temps. I used a 240 volt 15 amp relay and put the active for my heating bulb on the NC pin of the relay. Now as summer is coming on one is also going to need to protect against high temps so I'll be changing fridges for my brew and use my old gas fridge with the resistive heating element. The active off this fridge will go to the NO pin on the relay and as the temp controller has a one degree hysterious I have it set to turn on at 23C and it will switch off at 24C. Now to power the relay I used a 12 volt plug pack which is 17.5 volts open circuit and made a 12 volt supply using a 7812 volt regulator on veroboard. The 12 volt line went straight to the relay coil and the negative goes to one contact on the temp controller, the other contact on the temp controller goes to the relay coil so when the temp point is reached the external relay will do the switching.

When I do get the other fridge all setup I'll take a couple of pic's and I do think this is a real cheap way for a temp controlled brew setup.

Cheers Bryan

RuddyCrazy wrote: Now to power the relay I used a 12 volt plug pack which is 17.5 volts open circuit and made a 12 volt supply using a 7812 volt regulator on veroboard. The 12 volt line went straight to the relay coil and the negative goes to one contact on the temp controller, the other contact on the temp controller goes to the relay coil so when the temp point is reached the external relay will do the switching.

Sounds like a sweet deal on the controller Bryan.

You have 12v going to one side of the relay coil. I'm not sure from your description, do you have a negative (0v) going to the other side of the coil?

emnpaul wrote:

RuddyCrazy wrote: Now to power the relay I used a 12 volt plug pack which is 17.5 volts open circuit and made a 12 volt supply using a 7812 volt regulator on veroboard. The 12 volt line went straight to the relay coil and the negative goes to one contact on the temp controller, the other contact on the temp controller goes to the relay coil so when the temp point is reached the external relay will do the switching.

Sounds like a sweet deal on the controller Bryan.

You have 12v going to one side of the relay coil. I'm not sure from your description, do you have a negative (0v) going to the other side of the coil?

Hi Paul,
Ok the 12 volt positive wire from the regulator goes straight to the relay coil, now the negative of the relay coil goes to the relay connection on the temp controller board and the negative from the regulator goes to the other contact on the temp controller. The relay on the temp controller is NO (normally open) so the external relay will only turn on when the temp controller reaches the set point . As the relay on the board will be NC (normally closed) the ground path for the 12 volts will be connected so the external relay will switch on.

I have set the active wire for the light bulb on the NC pin on the external relay and the neutral wire is connected directly to the mains input. I will state as this is dealing with mains voltage to be extra careful as one could easily end up pushing up daisies if one is careless.

I'll draw up a schematic so the circuit will be clear.

Cheers Bryan

Sorry mate. I shouldn't have doubted you. Just for a minute there I thought you had your coil in series with your probe or something.

No diagram necessary.

Will be interested to see your setup pics of this, sounds cheap, but if it works then I guess its all good.