- Jan 1, 1970
The ultrasonic circuit link below has two transistors that I can't
locate - SL100 and the SK100. I'm thinking of replacing them with
BD139 and BD140. Can anyone suggest better replacements than these?
What kind of supply filtering is needed when using batteries instead
of an adapter "wall wart"?
Which is the common trace on the transmitters tranducer and as the
transducers I have are the combined transmitter/receiver type will
this cause a problem with these circuits?
I'd be very inclined just to use more of the BC548/BC558's. They're easily
good for the 20ma's or so needed for the tweeter and relay.
What should have been shown on the diagram for both ac adapter use and/or
batteries is something in the area of a 220uF 16V capacitor across each of
the DC rails. In fact, in the case of the sender, I'd say without one you're
nearly guaranteed spurious oscillation.
Wouldn't have thought it matters which way round the transmitter transducer
is connected. With a combined TX RX the best way to go is just to try it.
The main problem would be sound cross coupling but that would have been for
the manufacturers to sort out in the first place. (that is assuming the
module is designed to send -and- receive at the same time)