Need to convert a constant output voltage to single pulse, and then again with reverse polarity.

Thread Starter

Nealieboyee

Joined May 24, 2017
56
Don't need an IC (yet). I'll use an additional mosfet.


Ok.

Does the timer output go high at night and low during day? Or does it matter to you?
Yeah it goes high when programmed ON time is reached, which is at night. During the day the timer is programmed to be off.
 

eetech00

Joined Jun 8, 2013
3,418
OK. Here is a "Preliminary" design with the LDR addition.
I still have to work out the LDR sensor design. It should have a pot to adjust the threshold.

The LDR has high resistance when dark and low resistance when light is sensed. This changes the REF voltage sensed by the TLV431. The TLV431 is configured as a comparator and monitors the REF voltage. Its internal 1.25 voltage reference is compared against the voltage at "REF". When this voltage exceeds 1.25v, the "LDO" output goes Low. This turns on M4 and if the Timer output is high, the selenoid will toggle and turn on the load. Likewise, if the either the Timer output goes low, or, the LDO output goes high, the selenoid should toggle again and shut off the load.

The whole circuit is designed to operate with a 6v supply and consumes about 750uA (not counting selenoid operate current).
If you still want to continue, I'll plan to tested the Light sensor portion but plan to tomorrow.

1624828689024.png
 

Thread Starter

Nealieboyee

Joined May 24, 2017
56
OK. Here is a "Preliminary" design with the LDR addition.
I still have to work out the LDR sensor design. It should have a pot to adjust the threshold.

The LDR has high resistance when dark and low resistance when light is sensed. This changes the REF voltage sensed by the TLV431. The TLV431 is configured as a comparator and monitors the REF voltage. Its internal 1.25 voltage reference is compared against the voltage at "REF". When this voltage exceeds 1.25v, the "LDO" output goes Low. This turns on M4 and if the Timer output is high, the selenoid will toggle and turn on the load. Likewise, if the either the Timer output goes low, or, the LDO output goes high, the selenoid should toggle again and shut off the load.

The whole circuit is designed to operate with a 6v supply and consumes about 750uA (not counting selenoid operate current).
If you still want to continue, I'll plan to tested the Light sensor portion but plan to tomorrow.

View attachment 242288
Wow you work fast. Thank you so much. Yes I'd very much appreciate if you could test it. 750uA sounds really good in theory.
 
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