Thanks for the answers guys, I was out for a few days, so late follow-up. By
the way, the transformer is really that small, its a mains transformer in a
blue plastic shield, about the size of a grape. It was very cheap also,
about $1. I can mail you a picture of it if you want
I bought these small transformers in a local store. I plan to build my own
home automation system and I want to place small RF controlled relays around
my house, between the electrical-outlets and the appliances. I need to
provide the RF receivers and the logic with appropriate voltage, so I
thought a really tiny 6V transf. would be the thing. I guess 29mA is enough
to power some simple RF receiver from Laipac etc..
I just saw an article in an Electronics Magazine that described a extremely
useful small circuit to step-down the mains voltage to TTL level by just
using a X2 safety capictor, a FET and a few compos, no transformator.
Perhaps i should just use that instead.
Anyway, the concept of powerfactor confused me at first because I read that
powersupply equipment is often given a powerfactor rating. So is such a
rating typically given for a particular load or ampere usage? Let me follow
up on that a bit so I get this right.
When a load is purely resistive the powerfactor is 1, right? So the reason
we have the concept of apparent power and real power is the
inductive/capacitive characteristics of a load. I read that if my load has a
capacitive reactance I should be able to add some coil/inductance to
compensate/cancel out that, in theory at least.
So, if I build a simple powersupply with my transformator, using a full
rectifier and a filter cap (no regulator), can you comment on the following
- Assuming the Cap is a big electrolyte, the powerfactor I get when
connecting a resistive load would be a good indication of the quality of my
transformer?
- If the transformer and the cap where "ideal", I could select the cap to
"match" my transformer so that my setup would have powerfactor 1?
Also, can I combine the two taps in some way to get one 6V output with
double VA rating, thus 2x0.175VA ?
Put a 30 ohm load on it and see what it does. What is the output voltage
loaded and unloaded and how warm does it get after an hour or so? That
should answer your question.
Wouldn't that mean that I = Vrms/30, or more than 100mA? That should surely
make it hot yes...
What is the likely senario when overloading a transformator like this? I
guess the heat can melt the isolation on the copper wires and create a short
circuit in the windings?
I think I need to set up a few things in my work environment before I start
fooling around with mains stuff. Rubber gloves and mat comes to mind
cheers,
erik