thyristors in a display circuit

[law4eva]

please can anyone help?
I need to use thyristors in a display (sequencial )Circuit
to light ac load (bulbs) rated 240v,60w instead of LED's.
Each time I try to simulate, the thyristor latches thus keeping the bulbs lighting continuously.
All help is urgently needed.

 

[nbucska]

HOW do you simulate it ?

<nbucska@pcperipherals.com>

 

[piedade]

hi ... i supose you're simulating in a real enviorement... not in a pc ok ?
is so ... you may be using a thyristor with a very low Vrm and in that case when you conect it to the 230v mains it latches automaticaly without the need of firing inpulse aplied to the gate.
i recomend you get a part for 500v or 600v
now about the use of the thyristor ... unless you're using a full bridge rectifier circuit you're going to loose half of the power.
Try to use an TRIAC instead example
BT137D / 600v
the &quot;D&quot; needs less trigger current its beter for aplications where you want to control it directly from a digital circuit. if it's not the case the standard version BT137 is suficient ... this triac can stand up to 8Amp. with a suitable dissipator. hope this info can help you

 

[Chuckles159]

Are you sure the simulator is running the thyristors on AC and not DC?

 

[law4eva]

hi piedad
thanks for that hint. it worked!