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outctrl

New Member
After I posted, thought that was stupid. Have a machine that when it comes out of auto cycle, it puts out a pulsing signal that flashes a light on and off. The light got replaced with a tower light, so instead of just a green light going on and off, it now flashes two lights, green and yellow alternately. Would like to make pulse solid to keep on just one light. Hope this makes more sense. Thank you. Oh, 5 volts
 

gophert

Well-Known Member
Most Helpful Member
You can google "retriggerable 555 timer (most likely answer most people will turn to first) but there are some issues.
I would use the very easy (two external components (1 cap, 1 resistor) for the timing, using a retriggerable astable CD4528.

use cap and resistor to set timing just slightly longer than the flash of either light. More circuitry will be required if you need this to turn off at the exact same time as the alternating flasher - otherwise the simple solution here turns off about one flash pulse late.

The output drive (current limit) is quite low so you'll need an NPN transistor as a low-side switch.
 

AnalogKid

Well-Known Member
Most Helpful Member
Ir sounds like the light has a circuit inside to turn the activation signal into alternating signals for the two colors. Are you asking about modifying the internal circuit so only one light comes on?

ak
 
Last edited:

outctrl

New Member
Thank you. Actually I/O board putting out pulse that turned on and off green light. No schematic on board. When tower light added, a relay was put in place of light, using no and nc contacts to change from green to yellow. When in cycle, pulse is solid 5 volts turning on relay, turning on green light. Cycle done, pulse on and off, turning on and turning off relay, cycles green and yellow lights. Would like to have either solid off or on.
 

crutschow

Well-Known Member
Most Helpful Member
A simple circuit that may work would use a diode and capacitor.

What is the approximate flash frequency?
 

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