A Bridge Replacement A Good Idea?

of

But a bridge is only four leads, instead of 8.

Go with the bridge. It's only one part, too, instead of four. :-)

Cheers! Rich

How soon is the next joke going to be? Like the cat that ate the cheese and sat by the mousehole, I'm waiting with baited breath.

Well, I'd rather see an opto SCR than a triac, since it _is_ switching an SCR, and it's DC.

Cheers! Rich

Hey Phil, When trigging SCRs the trigger voltage is applied from Gate to Cathode, not Anode to Gate. As shown, smoke city. YMMV. Harry

No, it's not smoke city. When the trigger SCR fires, it completes a circuit between the gate and the anode, which will cause a voltage to appear at the gate with respect to the cathode. Of course, the SCR fires in its switching time, the anode voltage plummets to VSAT, or whatever it's called, and the gate voltage just drops with it.

I did that for phase control in a 24V, 40A battery charger once. The controller board had a 68HC11 and some pots and switches and opto SCRs. I tied the opto SCRs' anodes to the anodes of the main SCRs, and their cathodes to the gates. I used twisted pairs from the PCB to the SCRs, and it worked like a champ. Short-circuit-proof, too, which I kinda had my trepidations about - what I did was measured the output voltage and current, and just fired the SCRs at the right time in the half-cycle, and in any given half-cycle either was too far above where it should have been, the uP just quit issuing firing pulses, so it'd last a half-cycle, at most.

Cheers! Rich

Huh?

Thanks, Rich

Well, okay, but suppose I'm happier with a 2.2A, 2.5A or a 3A diode if it is 1/10 the price or has a lower voltage drop. Basically,it's pretty useless. Compare Digikey, who appear to have actual humans (presumably) on staff (or perhaps outsourced in Bangalore) who both understand IT and understand their customers.

Best regards, Spehro Pefhany

No smoke at all !

That method is fine. It shows trigger current from V+ being injected into the gate. Note the 180R.

Where would you propose getting the trigger current from ?

Graham

From a brief look, similar. Both have some irritations in their organization of products; both are much, much better than nothing. Farnell allows you to sort by unit price, which is nice (but perhaps not always indicative of quantity prices). Digikey just doesn't allow it.

Similar strategy.

That's a good idea.

Best regards, Spehro Pefhany

while back I had a small

metal film R as combined R

sub-contractor couldn't find

'blowing', so it's back to a

There are things like this:

I believe there are cheaper generic parts like these Taiwan ones:

I used them in a supply for a product some years ago, but don't have easy access to the BOM.

Best regards, Spehro Pefhany

I believe opto SCRs are a bit thin on the ground though.

Graham

Huh ?

Graham

I believe that opto-SCRs are rather less well represented in the distributors' portfolio than opto-triacs. Does that make sense ?

" thin on the ground " = few

' my troops are thin on the ground ' for example.....

time

I'd be interested to see what you think of Farnell.

Not greatly price competitive but stocks in depth with excellent data.

They do have a separate distribution compamy that can serve your production requirements at a more economical price too.

Graham

while back I had a small

power metal film R as combined R

sub-contractor couldn't find

'blowing', so it's back to a

LOL !

Might have guessed it was Vishay ! Then again what *isn't* Vishay in passives these days ?

I ought to take a look I guess !

They look like the classic cement W/W Rs to me. Don't see any fusible data.

Thanks anyway.

Graham

"Harry Dellamano"

See figure 6 on the data sheet:

I reckon it will work OK to dump the 5 mJ of energy from that 100 nF cap a few times second.

............. Phil