 |
 |
| View previous topic :: View next topic |
| Author |
Message |
Ttelmah
Joined: 11 Mar 2010
Posts: 20061
|
|
 Posted: Sun Mar 27, 2016 2:52 am |
 |
|
1) Redesign your zero crossing circuit. It won't be reliable with real mains. Unfortunately, in a real building, there will be nasty spikes on the mains (many from other triac's !), and so getting a really reliable zero voltage detection is quite complex. Much better to use well designed circuits for this....
2) Switch to using a snubberless triac. Without a snubber, it is easy to overvoltage the triac, even into loads you think are non inductive. Using an external snubber then adds the problem that if this is too large, it draws significant current, while if it is too small it doesn't protect the triac. Spurious switching is a fairly sure sign that there is a problem with the snubbing, though it could also be the gate floating (below).
3) Add a resistor between the gate and the bottom of the triac. Without this many triacs will not reliably stay off. |
|
 |
temtronic
Joined: 01 Jul 2010
Posts: 9632
Location: Greensville,Ontario
|
|
| Posted: Sun Mar 27, 2016 6:22 am |
|
|
Maybe I'm missing 'something' but that LED light shows a 4k7 in series with 2 x 56r, so 4727r as a load. Really not sure why the 27r ?
18 white LEDS at 3.4 v is about 60 volts overall
also where's the current limiting for the LEDs ? Unless the 4k7 is just the load and the 56rs are really in series with the LEDs ?
Jay |
|
|
tienchuan
Joined: 25 Aug 2009
Posts: 175
|
|
| Posted: Sun Mar 27, 2016 8:04 am |
|
|
| Ttelmah wrote: | 1) Redesign your zero crossing circuit. It won't be reliable with real mains. Unfortunately, in a real building, there will be nasty spikes on the mains (many from other triac's !), and so getting a really reliable zero voltage detection is quite complex. Much better to use well designed circuits for this....
2) Switch to using a snubberless triac. Without a snubber, it is easy to overvoltage the triac, even into loads you think are non inductive. Using an external snubber then adds the problem that if this is too large, it draws significant current, while if it is too small it doesn't protect the triac. Spurious switching is a fairly sure sign that there is a problem with the snubbing, though it could also be the gate floating (below).
3) Add a resistor between the gate and the bottom of the triac. Without this many triacs will not reliably stay off. |
Thanks for your helping.
_Really the zero crossing detect circuit block, Im get on whitepaper on EDN magazine, also I tested with real circuit and the result is good, sothat I dont think an errors beside in this block. If you see any problems in this circuit
block, please show me points in this.
_Yes, I think a good way, because the last circuit you give I choose a value not right, I'll looking a way to calculate for this component, also Should I change to another type of this snubber( an datasheet of TRIAC BTA12 have an another snubber circuit)
And I dont known will be have a problems when connect load to T1 or T2 pin of TRIAC.
_yes, i also added the resistor between T1 and gate in the last tried.
Thanks you
_________________
Begin Begin Begin !!! |
|
|
tienchuan
Joined: 25 Aug 2009
Posts: 175
|
|
| Posted: Sun Mar 27, 2016 8:07 am |
|
|
| temtronic wrote: | Maybe I'm missing 'something' but that LED light shows a 4k7 in series with 2 x 56r, so 4727r as a load. Really not sure why the 27r ?
18 white LEDS at 3.4 v is about 60 volts overall
also where's the current limiting for the LEDs ? Unless the 4k7 is just the load and the 56rs are really in series with the LEDs ?
Jay |
UHMM:D
I dont design this led bulbs, I only buy it and unplugged to draw an schematic, may be an not good products.
Thanks.
_________________
Begin Begin Begin !!! |
|
|
tienchuan
Joined: 25 Aug 2009
Posts: 175
|
|
| Posted: Wed Mar 30, 2016 1:51 am |
|
|
Hi everybody.
I tried with another type with snubber circuit but the result dont change.
It fire Triac when driver Triac like as an above method.
And I think the problems from capacitor of light led bulb, it discharge when main lines off, make the zero point detect's failing -> the pulse on/off is wrong-> make dv/dt large than limit of BTA12 Triac.
I'll check the voltage on T1,T2 of Triac on the nextweek in Lab.
And I want to known,, if the error is it, Can I dimmer the led light bulb with this circuit?
Thanks you.
_________________
Begin Begin Begin !!! |
|
|
Ttelmah
Joined: 11 Mar 2010
Posts: 20061
|
|
| Posted: Wed Mar 30, 2016 3:05 am |
|
|
You have suddenly introduced "capacitor of light led bulb". What on earth makes you think you can dim an LED bulb like this with a normal TRIAC dimmer?......
Most LED light bulbs will not dim. If they will, they require a dimmer specifically designed for LED lighting. Not a standard TRIAC dimmer. The LED's that advertise themselves as 'dimmable', usually have huge coda about what types of dimmer are compatible.
Have a look here:
<http://www.edn.com/design/led/4368149/Efficient-method-for-interfacing-TRIAC-dimmers-and-LEDs-4368149>
It is actually much easier to dim LED's with GTO thyristors or MOSFET's, than with TRIAC's |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ 
Search
Register
Profile 
Log in to check your private messages 
Log in
