Need help identifying parts on this schematic (urgent)

[dynamite]

Hey all, i am in the works of replicating stan mayers demo unit.
i have already built his PWM not i need to build the regulation circuit.

i know the 78xx regulators have a max input of 35v, and they have a min input of +2v (approx)

what transformer do i need. at first i thought 35v but that seems to be alot of wasted energy.
and the caps wouldn't catch any spikes that might come thru (i'm assuming thats what they are there for.

and lastly the rectifying bridge, make it out of diodes?, if so, what value.
or just use one of the all in one peice's?

[WCastle]

Using a full wave bridge that has a current rating greater than
what the circuit needs could be fed with a transformer that
has an output near your "highest" volatge regulator's
output.

If you were using a single diode or a half wave bridge then that would
decrease your "RMS" or usable voltage, which would require a higher voltage
transformer.

So it looks like a (no lower than) 12vac transformer going into that full wave bridge, filtered
with capacitors should result in a "stiff" enough supply for your regulators.

The main things to observe here would be
1 what is the max current to the load?
2 make sure the bridge exceeds that.
3 make sure the ripple filters are stiff enough.
4 3 pin "chip" regulators need bigger heat sinks, in direct relation to how much
voltage you drop across them.


ie ; a 35v supply regulated by a 7805 means you are dropping 30 v across it
if you think of a 78xx as an "automatic variable resistor" then you can see how a 35v supply is overkill.

[dynamite]

ok, so a 15v -18v ac transformer would suffice happily?
i'm going to use a full wave bridge, i was just wondering if i should use 4 diodes of a one peice rectifyer?

i knew 35 was going to be huge over kill, just thought someone smater than me(like your self) could shed some light on the situation.

all they are powering is a 555, 3x 7490's and a 7404 (it's basically the pwm)

[topsykrett]

what are you going to use for an optocouple and scr for that circuit do you have part numbers

the scr is odd in the circuit it has postive in and out of it and the gate is trigger by positive i am no electronics expert but i dont think they make a scr like that i have been looking for a few days all i can find is a pnp npn is their something else out their i havent seen or dont know about

any help would be appreciated

[dynamite]

i havn't tried sourceing the scr just yet, but will let you know how i get along.

Edit:
from what i have read, this should suffice:
SCR TYN816 800V 16A T0220 Case (Z4333) - Dick Smith Electronics - New Zealand

[dynamite]

i just found a 240v-20.5v ac transformer in an old ac adapter, too grunty for those regulators? or just right?