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My lamp dimmer has a flicker when on low.

TommyR

May 13, 2010
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I found this circuit on the web build it and it worked but when first turned on with the control all the way in the low position the bulb lights up very dim, which is good, but there is a flicker. When I turn the control up the bulb brightens and the flicker eventually goes away. By and large if functions fine but I'd like to get rid of that turn on flicker.
Any help would be greatly appreciated. The Diac and Triac are ones I had and not the ones mentioned in the original schematic. The circuit was originally meant to control a soldering iron.
 

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Harald Kapp

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An unusal circuit for a lamp dimmer. The ones I know are usually like the one shown here:
1666350825165.png
Notice the different position of the load/lamp.

Question: hat kind of light bulb are you using? Tungsten filament, fluorescent, LED?
 

TommyR

May 13, 2010
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Hi: It's a Tungsten filament light bulb.
Your circuit is for 220V. Would R1 value change for 125V ? Also what would the value of VR1 be?
 

Harald Kapp

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Use the same values for R1 and Vr as in your schematic, then the circuit should be good for 125 V, too.
 

73's de Edd

Aug 21, 2015
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I'd say that would do it.
With the lamp in the present position its variable resistance and its shift, is screwing with the R1 VR1 voltage sourcing.'
With it in the triac A1 leg its isolated.
 

TommyR

May 13, 2010
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I'd say that would do it.
With the lamp in the present position its variable resistance and its shift, is screwing with the R1 VR1 voltage sourcing.'
With it in the triac A1 leg its isolated.
Ok sounds I'll try it.
The help is appreciated.
 

TommyR

May 13, 2010
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Ok sounds I'll try it.
The help is appreciated.
Using the new schematic suggested and trying different values for both R1 and VR1 I managed to have it operate the same as my bed lamp dimmer. Working on it today 4.7k with the 100k pot was not working as I wanted it to. Changing R1 value helped somewhat but not what I wanted. I then changed VR1 to 200k better but still not good even with changing R1 to a different value what did the trick was to go back to the originally suggested R1 at 4.7k and then using a 250k pot that made it operate just like my bed lamp dimmer.
Low end worked fine no flicker and just like my bed lamp dimmer you have to turn it on bring it up till it lights the bulb then back down to a very low level with no flicker. Top end applied 118vac to bulb just like my bed lamp dimmer.
Still using my original Triac BT136-600 [Amazon] and Diac DB3 [eBay].
Thanks to all for the help it put me on the right track.
 

TommyR

May 13, 2010
10
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Using the new schematic suggested and trying different values for both R1 and VR1 I managed to have it operate the same as my bed lamp dimmer. Working on it today 4.7k with the 100k pot was not working as I wanted it to. Changing R1 value helped somewhat but not what I wanted. I then changed VR1 to 200k better but still not good even with changing R1 to a different value what did the trick was to go back to the originally suggested R1 at 4.7k and then using a 250k pot that made it operate just like my bed lamp dimmer.
Low end worked fine no flicker and just like my bed lamp dimmer you have to turn it on bring it up till it lights the bulb then back down to a very low level with no flicker. Top end applied 118vac to bulb just like my bed lamp dimmer.
Still using my original Triac BT136-600 [Amazon] and Diac DB3 [eBay].
Thanks to all for the help it put me on the right track.
Let me add the final schematic that seems to work fine.
 

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