"Offbreed" wrote in
oups.com:

I cannot relocate the circuit,


Oops....I forgot to mention a problem with DC motor driving with this
latch. DC commutator motors don't draw current through the whole
rotation, just when the commutators make contact. So, you'll be feeding
pulsating DC to the SCR, which WILL ASSUREDLY make it unlatch! The cure
to the problem is to put a 100 ohm, 5 watt resistor right across the
motor, so that when the motor commutator opens, the SCR has a holding
current through the 100 ohm resistor to keep it latched, insuring a
steady flow of holding current until the lower switch opens.

By the way, I used this same exact circuit to power the motor of an old
8-track tape player loaded with 200 different ID messages for a ham
repeater back in the 1970s. Instead of the pump, it used the tape motor
drive. Instead of the upper switch, it used a keying pulse from an IC
timer that was only powered when the repeater was in use so we could all
sleep with our radios on. Instead of a lower switch, it had a normally
closed relay whos DC coil was hooked to a simple rectifier/capacitor
that turned the Channel 2 tape audio into DC to key the relay from the
right channel speaker output. Left channel 1 speaker audio was volume
controlled and sent the hilarious ID audio to the repeater transmitter
audio input.

After the repeater had been on the air 9 minutes, the timer fired the
SCR, which latched to play the tape. One of our hams had a girlfriend
who thought Levis should be cut off at the bottom of the back pockets,
and had the body to make everyone agree on the "ID Team". Her sexy
voice was the talk of ham radio up and down I-95 for years. One of the
team members was an F-4 recon pilot at Shaw AFB, SC. We took his
professional REVOX tape deck and fancy microphones out to the
flightline. His buddy flew the F-4 in full afterburner across the deck
making a terrible racket, complete with fantastic Doppler shift for
several tracks. You'd hear the repeater key and a faint jet engine in
the distance. Very soon, the jet got louder and finally zoomed
deafeningly by at 400 knots and out of range when the sexy girl would
say, "Welcome to Shaw Air Force Base! WR4AOI Repeater. Sumter, South
Carolina." (at this exact point a kid's whistle played silently to the
audience on the other channel, keying the relay and dropping the SCR
latch. At the end of the short tone, the next ID began on Channel 1,
something totally different like, "Oh, honey, now STOP THAT! It's time
to ID the repeater! WR4AOI Repeater, Sumter!" (another tone to unlatch
the SCR as the flywheeled capstan coasted rapidly to a stop, waiting for
the next ID-timer pulse......The finest repeater ID machine that cost
less than $2 with a trashcan tape deck. ONE track of the 4 on the cart
was all we had IDs for. The last ID was not at the end of the track, so
at that point the tape was left running to the unkeying beep at the end
of the tape loop, to repeat all 200 IDs over again in about 8 days!
Eveyrone enjoyed it so much they had me set it up to override boring
conversations on the repeater so noone would miss any...(c; A sound
effects record from WFIG-AM's studio allowed us to have lots of
interesting old-time-radio IDs, especially at Christmas/Halloween/4th of
July/Sumter local fair when we swapped out the normal 8-track cart for
the "seasonal ID carts" to commemorate the occasions. Our Santa, W4GL,
had messages for bad boys, bad girls, etc. The Halloween tape, of
course, was quite spooky with creaking doors, screaming women...oh, love
those screaming women....and things that go bump in the night...(c;

73 DE W4CSC....ex WR4AOI - 146.64 downshift sysop...(c;