BTA12 Triac Dimmer for Bulbs

[manoj.patil.1974]

Hi,
Thanks for the response guys !

This time, I purchased BT138 and BT139.

The dimmer now works perfectly fine with a 470K pot. Adding the hysterisis circuit results into a visibily gradual dimming as compared to sudden pop up of the bulb when its not connected.

The BT138 had smoke for a 1000W heater coil (new load), but then it did not get damaged. It works fine for the 100W bulb again. The tab appears black and plastic like..

The BT139 800E works perfectly fine for a 1500w heater coil. The heatsink gets really hot so looks like I have to work a bit more on the snubber circuit and heatsink calculations. Any good tutorial/note that can help me with best practices ?

I did not want to give up on the BTA16 though, so I brought a MJE13001 high voltage transistor. The diac was connected to the MJE base via 4.7K resistor. Collector to the main line via 600ohms and the emitter directly to the gate of BTA16. My attempt here was kind-of to amplify the gate drive current, but the bulb was Full on for any value of resistor in the RC network.... looks like I have to relook at the calculations and also there may be more things happening in this AC network and amplification may not be as simple as adding a transistor.

 

[em2006]

...This time, I purchased BT138 and BT139.
The dimmer now works perfectly fine with a 470K pot....

Now, will increase the values of R1 and R2 to 33-100K (your power supply is 230V), in addition, you put a wire instead of R8.

...I have to work a bit more on the snubber circuit... Any good tutorial/note that can help me with best practices ?...

Some references related to snubber network, if you intend to use inductive loads:

http://www.st.com/stonline/products/literature/an/6785.pdf
http://www.st.com/stonline/products/literature/an/3577.pdf
**broken link removed**
http://www.fairchildsemi.com/an/AN/AN-3008.pdf
http://www.onsemi.com/pub_link/Collateral/AN1048-D.PDF

 

[blueroomelectronics]

Incandescent bulb dimmers will someday be a thing of the past as many places are getting rid of them in favor of modern energy saving florescent replacements.
Simple dimmers without snubbers put out massive RF noise.

 

[ccurtis]

Manoj, I'm happy you have success after all the frustration.

Looking at the datasheets for the types of triacs you are using, a 1500W load will dissipate as much as 8 watts in the triac at full brightness. With a junction to ambient thermal resistance of 60 deg C per watt, that's 480 deg C junction temp (8W times 60 deg C) without a heat sink (even for the BT139). Smoke city! That requires some serious attention to heatsinking, snubber or no snubber. Based on the temp data in the datasheet, I figure your heatsink should have a mounting surface to ambient thermal resistance of no more than 13 deg C per watt (limiting value). This is figured as follows:

Max junction temp (150) - Junction to tab resistance × dissipation (2 × 8) - ambient temp (25) = max tab temp (109)​

max tab temp (109) ÷ dissipation (8) = max heat sink thermal resistance (13 deg C per watt)​

Preferably the heatsink should be 6 deg C per watt or less for a junction temp of 70 deg C (half the max junction temp)or less in free air. I would go for a heatsink of about 4 deg C per watt, or less for great reliability.

Your transistor idea, while admirable, won't work because the transistor is a unipolar device. I don't understand why the triac is full on, however, with that configuration, unless S1 is closed.

You can use a much smaller triac (with a more sensitive gate) to provide the high gate current for the BTA16. MT1 and MT2 of the smaller triac are connected across MT2 and the gate of the larger triac. The gate of the smaller triac is connected the same way as that of the larger triac was without the addition of the smaller triac.

 

[manoj.patil.1974]

Just a quick question. What are the triacs used for resistance (heater coil) loads in the range of 1500W to 2000W commonly used ? Basically, I guess my application needs a triac of 16A rating but lesser heat dissipation rating. I will also look around the various triac offerings from NXP Semiconductors

 

[ccurtis]

Your minimum required current rating for the triac is load power (watts) divided by the mains voltage. In your case 2000 watts ÷ 230 volts = 8.7 amps. So, a 12 or 16 amp triac is fine for your application. An 8 watt dissipation is very reasonable at that current, and I doubt you will find a triac that will dissipate much less power than that. I don't think you can get around a heatsink requirement with any package style, either. The triacs you have been using with success are good for the job. The fact that you need a heatsink is not a reflection of a poor choice of triac, but rather that you are driving a heavy load, and no device is 100% efficient.

 

[Gayan Soyza]

In my dimmers I always use TIC series triacs, ex TIC 210,TIC216 & never use BT & BTA series.

 

[mvs sarma]

Incandescent bulb dimmers will someday be a thing of the past as many places are getting rid of them in favor of modern energy saving florescent replacements.
Simple dimmers without snubbers put out massive RF noise.

I totally agree with Bill. I would like to add further. most CFL and Tube lights, Cell chargers TV power supplies, Fan regulators-- to generalize, most switching supplies have become an eyesore to any RF equipment and especially the DXRadio hobby
May be some medical equipments like pacemakers also likely sufferer of this interference.
This interference has been on high side and even the developed countries are suffering.
UK based DRM and amateur groups have sent mass representation to save them from interference caused by power supply adopters supplied with ADSL or DSL equipments.

 

[manoj.patil.1974]

Hi
Right, these kind of phase angle control power control will lead to RF interference. But how do these manufacturers get away with this ? Fortunately, I travel for my job so I have seen it in the USA, Canada, Singapore and my home country that the smaller devices used for dimming lamps/fans etc DO NOT have any kind of filters ( atleast the cheaper one's I saw and may be I did not break open the costlier one's). Especially the ceiling fan regulators are these days primarily thyristor based and they have kind of replaced the older one with big rotatry switch and internal large resistors.

I am curious, how did the UK based DRM mass representation go through ?

 

[mvs sarma]

Hi
Right, these kind of phase angle control power control will lead to RF interference. But how do these manufacturers get away with this ? Fortunately, I travel for my job so I have seen it in the USA, Canada, Singapore and my home country that the smaller devices used for dimming lamps/fans etc DO NOT have any kind of filters ( atleast the cheaper one's I saw and may be I did not break open the costlier one's). Especially the ceiling fan regulators are these days primarily thyristor based and they have kind of replaced the older one with big rotatry switch and internal large resistors.

I am curious, how did the UK based DRM mass representation go through ?

The link is here
Interference from BT Powerline adaptors: Save shortwave petition - DRM Software Radio Forums

 

[TopGunPilot]

Hi,
Thanks for the response guys !

This time, I purchased BT138 and BT139.

The dimmer now works perfectly fine with a 470K pot. Adding the hysterisis circuit results into a visibily gradual dimming as compared to sudden pop up of the bulb when its not connected.

The BT138 had smoke for a 1000W heater coil (new load), but then it did not get damaged. It works fine for the 100W bulb again. The tab appears black and plastic like..

The BT139 800E works perfectly fine for a 1500w heater coil. The heatsink gets really hot so looks like I have to work a bit more on the snubber circuit and heatsink calculations. Any good tutorial/note that can help me with best practices ?

I did not want to give up on the BTA16 though, so I brought a MJE13001 high voltage transistor. The diac was connected to the MJE base via 4.7K resistor. Collector to the main line via 600ohms and the emitter directly to the gate of BTA16. My attempt here was kind-of to amplify the gate drive current, but the bulb was Full on for any value of resistor in the RC network.... looks like I have to relook at the calculations and also there may be more things happening in this AC network and amplification may not be as simple as adding a transistor.

Manoj, congatulations!
What are the value of the R's?
Was it successful using BTA16?
I'd like to see the circuit diagram.

TGP

 

[Ubergeek63]

Hi,
Thanks for the response guys !

This time, I purchased BT138 and BT139.

The dimmer now works perfectly fine with a 470K pot. Adding the hysterisis circuit results into a visibily gradual dimming as compared to sudden pop up of the bulb when its not connected.

The BT138 had smoke for a 1000W heater coil (new load), but then it did not get damaged. It works fine for the 100W bulb again. The tab appears black and plastic like..

The BT139 800E works perfectly fine for a 1500w heater coil. The heatsink gets really hot so looks like I have to work a bit more on the snubber circuit and heatsink calculations. Any good tutorial/note that can help me with best practices ?

I did not want to give up on the BTA16 though, so I brought a MJE13001 high voltage transistor. The diac was connected to the MJE base via 4.7K resistor. Collector to the main line via 600ohms and the emitter directly to the gate of BTA16. My attempt here was kind-of to amplify the gate drive current, but the bulb was Full on for any value of resistor in the RC network.... looks like I have to relook at the calculations and also there may be more things happening in this AC network and amplification may not be as simple as adding a transistor.

There is no way around the heat generation. It is current times voltage and needs to be handled by the heat sink.

Snubbers are for inductive loads and are to prevent false triggering, again no help for the heat. (electric heaters are not inductive)

Dan

 

[cjbrown22]

i want to boost power a 2000w cooker or a 1.5 horse power air condition with a bta 26 600b triac transistor or better one. pls can somebody help me with circuit diagram