Maker Pro
Maker Pro

diac troubles in a heater circuit

tuneup

Jun 13, 2018
10
Joined
Jun 13, 2018
Messages
10
I have a rather simple circuit that controls heating elements. After testing each component, I find them all good except the r20 (47 ohms resistor And the diac.( the diac show a few ohms in each direction when tested with an ohm meter). I have replaced the 47 ohm resistor but don't have an idea of what diac would work in this circuit.
This is were my electronics stop and your help is needed.
This diac is the only component that I can't identify. I will add a circuit diagram I found that is wired exactly the same.
the component values are slightly different. they are:
r20 = 47 ohms
c24 = .224uf
triac = 56026
c23= .104uf
r19 = 1k ohms
vr4 = 0-500k ohms
diac = unkown
the load is a 240 volt heating element.
thanks for any help.
Rex
upload_2018-6-12_21-8-13.png
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
12,898
Joined
Nov 17, 2011
Messages
12,898
A typical diac has around 30 V to 40 V breaktrough voltage. In this circuit it is used to cerate a rising edge to trigger the triac. The absolute parameters of the diac are very likely not critical. Any off the shelf component should be usable.

btw: a bit misleading is the text giving R20 = 47 Ω but the schematic showing R20 = 100 Ω
 

tuneup

Jun 13, 2018
10
Joined
Jun 13, 2018
Messages
10
Thanks so much for the help and info. I ordered a db3 this morning.
Sorry I wasn't more clear for the drawing, it is one I found on the internet that just happens to be exactly as my circuit except for the values of the components. that is why the components were stated out.
thanks again.
 
Top