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[SOLVED] Dimmer problem.. help me

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manikandan123

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hi freds!
I want to build a triac dimmer by using Transformerless power supply. I am using common hot power supply. i am using PIC microcontroller to drive the Gate of triac BT136.i am aso having the Zero cross detection by using software algorithm.my problem is the bulb is not glow.i checked in simulation there is correct Pulse. And also one doubt in this load connection. we always do the ref is MT1.now i am connecting MT1 to the Neutral of Power supply and Phase to Load and other end of load to MT2.Please help me... how do use the Transformerless power supply in Load connection? :-| and also how do resolve this problem?.. how do make it Glow?

ww1.microchip.com/downloads/en/AppNotes/91094A.pdf i am using Capacitive transformerless power supply?
 
Last edited:

@mister_rf i am using this circuit. Please refer. But i am using capacitive transformerless power supply. i am doubt on load connection?.

ww1.microchip.com/downloads/en/AppNotes/91094A.pdf.
 

So when we choose a triac, we will want a small sensitive-gate triac capable of switching 4 amps. It should have a minimal hold current requirement so we can limit the amount of time that we will have to supply a gate current
Click to expand...
In this type of application, using a microcontroller to control the triac, they have used L4004D3
http://www.kkg.com.cn/product/TECCOR/L4004D3.pdf
So need to change the BT136 with some very high gate sensitivity triacs series,
http://www.raphnet.net/electronique/triac_lights/striacs.pdf

Read also here:
http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXyzyuv.pdf
 

its pretty good.But BT136 also one of the best Triac.ok. PIC controller is very useful to change the Program.then the transformer less power supply is not original dc wave form.it look like a dc. but it having the AC power in its output.May this AC affect the PIC or not?
 

Yes BT136 it’s a very good triac, but not to be used here for this nano-Watt application.
This application requires using triacs with a typical gate current drive of 3 mA and the minimum hold current is less than 5 mA.
 
Hi,
I did circuits like that. But as mister_rf has pointed out, you shouldn't attempt to use a BT136 here. Use a gate-sensitive triac. The current capacity of your circuit is limited by the power supply as well as the limited PIC drive current. So using a gate-sensitive triac means it requires less current to turn on. In all such circuits I made, I used BT134.

Hope this helps.
Tahmid.
 

Not even a BT134 usable in this circuit,need to have gate current drive of 3 mA and the minimum hold current less than 5 mA.
 

Didn't see the circuit first. To use BT134 or even BT136 you need to increase the current capacity of the power supply. A better power supply would be capacitor based. You say you already did that. Using a capacitor of 1uF, I've fired 3 BT134's without any problem.

Hope this helps.
Tahmid.

---------- Post added at 15:25 ---------- Previous post was at 15:24 ----------
mister_rf said:
Not even a BT134 usable in this circuit,need to have gate current drive of 3 mA and the minimum hold current less than 5 mA.
Click to expand...

Why 3mA and 5mA? He said that he changed the power supply to capacitive one. So, if his circuit (capacitor and resistor values selected appropriately) can supply more current, the PIC can give upto 20mA.
 

The idea whole of nano-watt technology it’s based on minimize power consumption also on microcontroller side, using short pulses to command triacs, but triacs should have a minimal hold current requirement so we can limit the amount of time that we will have to supply a gate current.
I don’t know how he had implemented this in his software, but I guess he’s trying to use this example:
**broken link removed**
 

Attachments

  • 91094A.pdf
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hi,
yes you r correct. i am also seeing many of the threads,the triac will be used depending upon the application. ok my doubt is series resistance with gate or gate control technique. i am using Capacitive transformerless powersupply.it will have 16mA.that is not problem.i am also complete to detect the Zero cross. actually the square wave is lead compare to original AC wave form.the code is ready. my doubt only on the load connection. i am using Common Hot power supply.where to i connect the MT1.the load should be always in MT2.its OK. where to i connect the MT1.all gate control must reference with MT1.may i connect MT1 to common hot side. or ground side of power supply... how do u connect it.. please provide some details.

---------- Post added at 18:27 ---------- Previous post was at 18:24 ----------

ok mister_rf.thanks for your commitment.please give some idea about load connection on Common Hot power supply...the sensitive gate Triac having 5mA. how do cotrol the power .. provide some details .
 

I couldn't reply you since I can't download anything directly from Microchip (and Texas Instruments).
So I couldn't have any clear idea about your circuit you like to apply.
 

Thank you for your reply. I couldn't open the new URL as well... sorry.
If it is just a circuit, couldn't it be uploaded here?
 

Thank you mister_rf... Do you mean his circuit could be found on "91094A.pdf‎".
 

I don’t know, need to have some schematics. Also better to read the previous thread.
 

mister_rf said:
I don’t know, need to have some schematics. Also better to read the previous thread.
Click to expand...

the circuit is same. in that circuit they use resistive transformerless power supply.In my case, i am using Capacitive Transformerless power supply.In the Gate control area they use 22k resistance only. K. i used the series resistance in my case,but the result is Flicker.and sometimes the bulb is not glow.do you suggest any IDEAS?
 

Try doing this test:

Remove the load at the triac output (caution: the other two terminals MT1 and Gate are at the same potential of the remained power line).

Let the terminal of R8 at the side of GP2 pin be low (software or connect to ground, negative).

Measure the voltage drop on R8 (1.2K going to the gate).

You will likely get about 4.3V
So the triggering current is:
4.3 / 1.2 = 3.6 mA

None of my triacs (rated for 4A load and above) can be triggered properly by this small current.

So try to add in parallel to R8 another 1.2K resistor. It would double the gate current. And test again if the lamp light is steady. If not add a third one... and so on. Obviously when the load is made on properly, you will replace all resistors with one of equivalent value.

Kerim

Edited:
If the GP2 pin cannot provide the necessary current, you will need to add a simple drive to reach the triggering gate current.
 

KerimF said:
Try doing this test:

Remove the load at the triac output (caution: the other two terminals MT1 and Gate are at the same potential of the remained power line).

Let the terminal of R8 at the side of GP2 pin be low (software or connect to ground, negative).

Measure the voltage drop on R8 (1.2K going to the gate).

You will likely get about 4.3V
So the triggering current is:
4.3 / 1.2 = 3.6 mA

None of my triacs (rated for 4A load and above) can be triggered properly by this small current.

So try to add in parallel to R8 another 1.2K resistor. It would double the gate current. And test again if the lamp light is steady. If not add a third one... and so on. Obviously when the load is made on properly, you will replace all resistors with one of equivalent value.

Kerim

Edited:
If the GP2 pin cannot provide the necessary current, you will need to add a simple drive to reach the triggering gate current.
Click to expand...

Thanks KerimF; i will do it.:!: somebody use NPN transistor to Gate control... is it necessary in -ve gate current.i am also take square wave in bottom side of the circuit. in my case phase of AC.How do know this is negative current?
 

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