Dc circuit help

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
I have a signal output on a sensor that is 5vdc when open and 0v dc when closed, I need to send a ground signal to my timer board when sensor is closed because the input on my timer board trigger needs to see a ground to be triggered, any help would be great thanks.
 

KeithWalker

Joined Jul 10, 2017
605
I have a signal output on a sensor that is 5vdc when open and 0v dc when closed, I need to send a ground signal to my timer board when sensor is closed because the input on my timer board trigger needs to see a ground to be triggered, any help would be great thanks.
That is very little information to work with. I will assume that you want to trigger your timer when the sensor detects an "open" (whatever that is). Are you detecting a physical event? Could the detector be relocated to detect the opposit? Do you have DC available to power a circuit if you build one to invert the signal?
Please give us a bit more information so that we can make some suggestions.
Regards,
Keith
 

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
I have an liquid optical sensor that has a 5vdc output when open and a 0vdc when closed (LGZD sensor v1.1)
I have a l298n H-drive motor board
And a dw44 ne555 4pin timer
12 volt power supply supply power for l298n board and 5v from the L298 board to supply the optical sensor board and the dw555 board power
The output of the optical board is 5vdc when open and 0vdc when closed the input on the dw44 needs a ground signal to start the timer, the output of dw44 is 5vdc goes to in2 of the L298 board to start the motor. And I need the timer to start when optical sensors is closed.
 

SamR

Joined Mar 19, 2019
1,650
Read the PDF! The 555 trigger pin 2 activates on LO input, not GND. For 5V Vcc the Min is 1.45V so it will be triggered on 0V.
 

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
Read the PDF! The 555 trigger pin 2 activates on LO input, not GND. For 5V Vcc the Min is 1.45V so it will be triggered on 0V.
Ok but when I have the output of optical sensor hooked up with it closed it has .395 v to ground but does not trigger the timer but if I ground out input of timer everything works as it should. Just looking for help I read the pdf and I know what it says the input needs but not working like that.
 

Audioguru again

Joined Oct 21, 2019
705
If the 555 timer is powered from +5V then a voltage lower than +1.67V on its trigger pin2 will trigger it. But it will not timeout until its pin 2 returns high.

Please post the schematic of your 555 timer.
 

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
When optical sensor senses water will trigger timer to start motor and water level will drop opening sensor thus sending voltage back on output of optical sensor to timer input
 

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Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
I need timer to run motor for a certain time.
I do have a float switch and I can get it to work by hooking one side to ground and the other to dw44 input.
but was trying to utilize the optical switch but if I can’t get optical to work will just use float switch
 

ericgibbs

Joined Jan 29, 2010
9,375
Look like that is switching from ground to power on that diagram
No, it is not.
The bottom of the left side 10k is at +Vs also the bottom of the Trig resistor is at +Vs
When the bottom of the left side is connected to 0V a LOW going pulse is created on the Trig pin, read the diagram I posted earlier.
E
 
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