Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

I'm Stuck on this thermostat.. Please help.

Status
Not open for further replies.
Luke,

My apologies for the delay ! It appears that the circuit is triggered 'ON'
ALL the time.

1. Is the Light(LOAD) is OFF when you disconnect pin 6 to the gate of the triac ?

Let's insure that pin 4 and pin are connected somewhere, And NOT left floating.

2. Tie pin 2 to Vcc with a 100K resistor for R3.

3. Tie pin 4 to Vcc with a 47K resistor(R1).

With these values the circuit should trigger at ~ -2.9V or >.

Try again ! Please attach the present form of the circuit with ALL part values.

Fred
 
SUCCESS!!!! (least I think so)

Hi Fred

Sorry for the late reply.

Well I think we have broken the back of this problem. When I reversed the ac wires earlier(as you advised) I did not change the wires for the triac. With this setup the light stayed on all the time.

I changed the wires to the triac and now it appears to work. The lamp flickers
when the sense voltage is around -2.75volts and it goes off at around -3.00volts and when it is really low eg: -1.0volt it is on constantly(just the occasional flicker).

I believe that I now just need to play around with the resistor values in the divider and It will be working.

I would like to add a fuse to this circuit( for safety), where should this be added?

THANK YOU FOR ALL YOUR HELP!!!!!

You have been so helpful.

I hope I am not jumping the gun with this circuit, I dont think I am.

Cheers

Luke
 
Luke,

Great call on observing to reverse the leads on the triac. (sorry that I missed that one) !

Now you know alot more about electronics. ( NTC thermisters, capacitors,
triacs, Leds, and breadboarding prototypes)

This is quite an accomplishment AND for a good cause...Python Eggs !

What made you think to change the triac leads ?

I would place the fuse (3AT @220VAC), in series with the 'HOT' lead that feeds the common connection Cathode of the 1N4004 and 300W bulb.

Are you O.K. with calculating the voltage divider 100K(NTC) and Rdef ?

The NTC @ x degrees C = x K ohm( say 100K @ 25C), Then
Rdef(4.7K)/ R ntc + 4.7K ~ 2.75V....the set point.

Take care of those Python eggs !

Cheers,

Fred
 
Hi Fred

Thanks for the compliments.

To be honest it was a bit of a guess. I just thought it had too be something with the triac. Everything else seemed ok. And with changing the supply wires I thought I might need to change where the gate fed from.

I should be ok with the calculations.

Thank you again for all your help and support. My pythons will benefit from your help.

Honestly I think forums such as this and the people on them such as yourself are what makes the internet so great.

I definately feel motivated to learn more about electronics now.

Thanks again

Luke

:D
 
Luke,

I am glad to hear that you are motivated with electronics !

Yes, I agree about this forum. I learned something too !

Take care,

Fred
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top