I am looking into using FK934 for my project but am wondering how it works. My project involves building a cooler using the peltier effect. I want to use the FK934 to control the temperature of the cooler. If the temp. is cooled to the temp. set on the thermostat, the power supply will cut off. When the temp. increases, the power supply will kick in to cool it back.

Can anyone advise on how I can do this with FK934? There doesn't seems to be a display screen, so how do I set the temp.?

 

Hello,

Do you hav a link to some more data on this FK934?
Without this we can not help you.

Greetings,
Bertus

 

I am so sorry. I wanted to post links but wondered if external links are allowed in this forum. Here you go...

http://store.qkits.com/moreinfo.cfm/FK934
http://store.qkits.com/images/fk934.gif
http://www.bakatronics.com/shop/item.aspx?itemid=649

If I am not wrong, FK stands for Future Kit Tech. Kit Set. Or at least, that's the manufacturer for the thermostat which I can get my hands on.

 

We need the schematic. Do you have a link?

 

Hello,

Unfortunately there is no "manual" for download on the pages.
I will have to guess how it works.

I hope I am right and you can do something with it.

Greetings,
Bertus

 

ok, I found the schematics. The quality is low but should be readable.

http://www.funnykit.co.kr/bemarket/shin/menual/fk934.pdf

 

Using AC like it does it isn't standardized. Most modern thermostats use a transformer to use low voltage AC.

The relay is the component most likely to wear out over time. It will take years, but it will eventually go.

The rest of the parts could last a very long time, but lots of bad things can happen to them over time, mainly involving static electricity. I've seen commercial units last decades, but had others (in my house) go after a couple of years. There is an element of chance in this.

 

Hello,

In the schematic there is this picture drawn:

The small pot sets the range and the large is a fine adjust.
There is indeed no display.

Greetings,
Bertus

 

I am not quite sure what is the power supply like. Is it 12VDC or 12VAC? The diagram puts an AC adapter, I am assuming I need an additional adapter to convert AC to DC. So bascially, I can run this thing off a battery (which is what I want)?

What does the AC out/in for? It is connected to COM and NO.

 

They may be thinking of using it to control the heater and/or air conditioner. Modern units also use low voltage AC, though it won't matter from your units point of view, a relay doesn't care if the voltage is lower.

 

I am so sorry. I wanted to post links but wondered if external links are allowed in this forum. Here you go...

http://store.qkits.com/moreinfo.cfm/FK934
http://store.qkits.com/images/fk934.gif
http://www.bakatronics.com/shop/item.aspx?itemid=649

If I am not wrong, FK stands for Future Kit Tech. Kit Set. Or at least, that's the manufacturer for the thermostat which I can get my hands on.

External links are permitted when they contribute directly to the thread's subject and when they are not peppered with commercial ads.

hgmjr

 

Thanks. So the AC IN/OUT is to be connected to the power supply for the air conditioning. Can it be used for DC too? My DIY cooler is powered by either DC or AC, so I need the thermostat to regulate both AC and DC (not at the same time). Do I need to mod the board to include DC too?

 

You mentioned a Peliter, how big a surface are you trying to heat / cool?

 

The cooler will have a volume of around 30cm x 20cm x 20cm (H).

 

Does this thermostat reduce the current when the temperature is reached or does it increase the resistance? I am looking to save power with the thermostat, so if it doesn't reduce the current drawn and instead uses resistors to dissipate the excess power, then thats not what I want.

 

the circuit board points out 12 volts + and -

the thermostat will shut the unit off when desired temp is reached and back on after deviation.

 

here you are, cost the same as your kit, has a display, is programmable and will be just as much of a project for you to hook up a power supply and relay.





Honeywell Basic Programmable Thermostat
Model # RTH221B Internet/Catalog # 100633100
Store SKU # 885848
$19.98/EA-Each




Quantity:

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This item cannot be shipped to the following state(s): HI,AK

this is from the home depot

 

the circuit board points out 12 volts + and -

the thermostat will shut the unit off when desired temp is reached and back on after deviation.

Thanks. I will be looking into the Honeywell one too.

 

A good analogy to consider is the way a shower valve works. This is the essence of a PID control; Proportional, Integral and Derivative, and is the best way to control any process, in this case, water temperature. This should be the basis for your design.
See www.expertune.com for a good tutorial on the subject.

Regards, DPW [ Everyone's knowledge is in-complete...Albert Einstein]