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SCR controlled bilge pump
"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; |
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