Temp Controller

[Brewmaster808]

Was trying to build a cheap controller, consist of a mosfet, pot, thermistor. Works fine till cross over point, than the relay chatters. Relay is stand type. Question is what the cheapest and simplest way to stop chatter? Would it be with a capacitor + resistor, or diode + zener diode? Also if know the values would be greatly appreciated. The line voltage under load is 11 volts and the coil of relay is 12 volts.

 

[kbekus]

not the cheapest sorry, but I'm not too skilled at this. I used a 555 as a monostable to do a similar thing with my heater thermo. Set it up so that it stayed on for a minute or two.

 

[sintax69]

capacitor + resistor for a ac coil relay
dioded for dc coil relay
but they are just for spikes smooth it out a bit, you may need a cct to switch it hard on 555 may work or op amp do you have a cct diagram

 

[Jye]

Not sure how to solve your problem

When I made mine I use an opamp with a variable resister for positive feed back which creates some hysteresis and allows me to change the temperature bandwidth.

When you get your thermostat up and going I would be interested in seeing the final circuit.

:beer:

 

[Brewmaster808]

Its is a dc relay coil, that has diode already. But the problem is as Jye mention, the hysteresis at the switch over point is the problem. Would like to keep as simple as possible and fix the problem by adding compent at relay coil. The best thought I have so far is add a rc time constent across the relay that would take 3-4 minutes to charge before switching. The temp controller is used to drive a relay that the contacts turn on a peltier.

 

[vlbaby]

brewmaster,
can you post a circuit diagram? It will make it a lot easier to help you if we knew how you have wired it up.


cheers

vlbaby.

 

[PistolPatch]

It sounds as though you've put a lot of work into your controller so you mightn't like this answer!

I used a Replacement Thermostat Beverage Cooler DR056 (Ranco VB7 - Bottle) from Oz Spares. I reckon it's probably only $30 as I had mine supplied and installed for $60. With your expertise, installation should take about a minute! The link below is to distributors of Oz Spares so you can find one closest to you to get a price.

http://www.stokes-aus.com.au/Content/templ...id=68&zoneid=12

 

[Jye]

Hey PP

What is the temp range of the thermostat?

 

[PistolPatch]

Hey Jye. I think -3 to +12.5.

I just pulled out the brochure which has yet another brand name on it - Varifix (Service Replacement Thermostat)! I waded through their PDF (the English version) which seems to have all languages except English!!! Seem to have a solution for a few temp. ranges though am unsure whether they have one suitable for fermenting both lagers and ales. Here's the link anyway...

http://www.invensyscontrolseurope.com/lwwc...STATS%20Bri.pdf

After reading that I think ringing Oz Spares would definitley be the go!

 

[Ducatiboy stu]

Personally I would go with the stokes/EGO thermo. Buy the 0-40*c unit with 2*c hysterisys and it will do either cooling or heating depending on wich way you set it up..( the Tobins unit is not as good as the stokes unit and about the same price..)

I am an electronics tradesman and I could not be bothered anymore designing ccts when I can buy something for $40 from TLE

I spent too many years dealing with relays, diodes, op-amps, transistors, caps...blah...blah ...blah..

I just want to make good beer now...

 

[Joel]

I got this excellent article from somewhere:

View attachment Electronic_Thermometers_for_Brewers.doc

When I built my thermostat (it is all about "homebrewing" isn't it?), I basically just followed the plans. Mine has an LCD temp readout with a switch so I can see the "set" temp and the actual temp.

My hysteresis is set a little too tight (only about 1 degree F), and I have a few mods that I'd like to do to it in the new year....

BTW. For heating operation just use the other relay contacts (the ones that don't go to the fridge) as they are in opposite operation to the ones that go to the fridge (if that makes sense).

 

[Brewmaster808]

Update: Yes the post listing the 555 would of been the smart way to done this. I used this link to build it. temp controller but using a relay when it switched to the normally open position it would chatter because of hysteresis, which the 555 would of eliminated. However, after thinking it over and the response recieved, I deciede get rid of the relay and go directly to peltier chip. The only change I see is to replace the mosfet IFR510 with a NTE2396 thats handles 28 amps. Hope my thinking is correct, alread purchased the mosfet. If it does than I have a corny fermenter like sold on B3 for around 50 - 60 bucks vice the 350 plus they want. I try to up date post when completed. But if anyone see problems let me know. Hate to replace peltier cause of over site.