Hi All
I want to build a theatre phone ringer. (UK 400ms On 200ms Off 400ms On 2000 ms Off)
I have found a lovely circuit (555/556 based) which does the job, and buzzes a buzzer. I actually want the timer to not buzz, but to instead drive a relay which sends pulses of 120V down the line to the phone on stage.
I bought a goody bag from Maplin and set about cataloging the bits I received, and in the bag was a K3020P, which I found a datasheet for. I thought that this was perfect, because it is a low voltage timer circuit switching a high level ring circuit, BUT, the K3020P switches AC. (see attached datasheet). I am a bit unfamiliar with AC, so I thought I would see what happened with low level DC at both ends. I built a test circuit (layout attached) and something starnge happens. If I turn on the switch, both LED's light, but If I turn off the switch LED2 stays alight. It will only go out if I break the circuit. When I rejoin the circuit the LED stays off.
1) What is happening?
2) If the pin 4 6 part of the circuit was DC would the circuit turn off when the 1 2 circuit turns off?
3) Is there a similar part which will switch high DC using low DC?
Sorry if this question is a bit niave
regards steve
I want to build a theatre phone ringer. (UK 400ms On 200ms Off 400ms On 2000 ms Off)
I have found a lovely circuit (555/556 based) which does the job, and buzzes a buzzer. I actually want the timer to not buzz, but to instead drive a relay which sends pulses of 120V down the line to the phone on stage.
I bought a goody bag from Maplin and set about cataloging the bits I received, and in the bag was a K3020P, which I found a datasheet for. I thought that this was perfect, because it is a low voltage timer circuit switching a high level ring circuit, BUT, the K3020P switches AC. (see attached datasheet). I am a bit unfamiliar with AC, so I thought I would see what happened with low level DC at both ends. I built a test circuit (layout attached) and something starnge happens. If I turn on the switch, both LED's light, but If I turn off the switch LED2 stays alight. It will only go out if I break the circuit. When I rejoin the circuit the LED stays off.
1) What is happening?
2) If the pin 4 6 part of the circuit was DC would the circuit turn off when the 1 2 circuit turns off?
3) Is there a similar part which will switch high DC using low DC?
Sorry if this question is a bit niave
regards steve
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