Hey all,
Newb here... I am building an LED dimmer/test circuit. This is for aircraft useage. I have my basic design, but want to put some finishing touches on it. It is basically a bunch of diodes for the push-to-test feature and a MC34060A chip driving some FETS that in turn drive the LED annunciators. The reason I made it is that some of the LED's need a reduced ground state and some need a reduced power state during night operation. I also want the night-time brightness level to be adjustable for all the LED's, thus the chip I chose. Here is my question... since this will be used in aircraft with either 14 VDC or 28 VDC input (with alternator running) what should I do in the way of protecting the power input to the FETS/chip/LED's? I was thinking of a 33V zener on DC input to the circuit. Is there a need to use capacitors to filter the DC input? If so, why and what size in mf? I also have a concern with the frequency of the IC (set to 600Hz) magically appearing in the aircrafts audio system. I have built a similar circuit in the past and it is audible in the intercom system, though very quiet. If you pull the circuit breaker to the dimmer the hum goes away. I did not filter or protect it in any way and it is still working after two years.
One more thing...anyone know of a web site that has a large selection of photocells? I am thinking of using a photocell so the pilot never has to select night operation; the annunciators will just dim auotmatically.
Thanks.
Newb here... I am building an LED dimmer/test circuit. This is for aircraft useage. I have my basic design, but want to put some finishing touches on it. It is basically a bunch of diodes for the push-to-test feature and a MC34060A chip driving some FETS that in turn drive the LED annunciators. The reason I made it is that some of the LED's need a reduced ground state and some need a reduced power state during night operation. I also want the night-time brightness level to be adjustable for all the LED's, thus the chip I chose. Here is my question... since this will be used in aircraft with either 14 VDC or 28 VDC input (with alternator running) what should I do in the way of protecting the power input to the FETS/chip/LED's? I was thinking of a 33V zener on DC input to the circuit. Is there a need to use capacitors to filter the DC input? If so, why and what size in mf? I also have a concern with the frequency of the IC (set to 600Hz) magically appearing in the aircrafts audio system. I have built a similar circuit in the past and it is audible in the intercom system, though very quiet. If you pull the circuit breaker to the dimmer the hum goes away. I did not filter or protect it in any way and it is still working after two years.
One more thing...anyone know of a web site that has a large selection of photocells? I am thinking of using a photocell so the pilot never has to select night operation; the annunciators will just dim auotmatically.
Thanks.