Dc circuit help

SamR

Joined Mar 19, 2019
1,802
Using a float switch requires a "snap switch" type mechanism to prevent "bouncing" ON/OFF about the level setpoint.
 

ericgibbs

Joined Jan 29, 2010
9,537
hi,
Your results, with V2 at 0.883v its never going to trigger the 555
What is V3 connected too.????


Your Results:
Sensor open
V1=5v Ok!
V2= .883v
V3= 2.1mv
Sensor closed
V1=.45v Ok!
V2=.883v
V3= 2.1mv
 

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
hi,
Your results, with V2 at 0.883v its never going to trigger the 555
What is V3 connected too.????


Your Results:
Sensor open
V1=5v Ok!
V2= .883v
V3= 2.1mv
Sensor closed
V1=.45v Ok!
V2=.883v
V3= 2.1mv
V3 is timer output goes to input on l298n which should have 5v on it when timer is active
 

MisterBill2

Joined Jan 23, 2018
5,186
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
USE AN INVERTER IC, such as a CD4049, or an equivalent. That will provide the inversion of the logic function and cost less than $1, which is about as cheap a fix as you can come up with. AND you can run all six of the sections in parallel and have a very large amount of pull-down. Just be sure to have the inverter common tied close to the timer common.
And there is a whole lot more to the timer than what is described, if that is what the picture is showing.
 

MisterBill2

Joined Jan 23, 2018
5,186
OK, ignore the suggestion to use an external IC to provide the logic inversion and provide a suitable pull-down to trigger the timer. Try a spice simulation and observe that it works.
 
Instead of guessing about a 555, why not look at its datasheet?

1) The trigger input pin2 needs a pullup resistor.
2) The timer will not time out if the switch remains turned on unless a capacitor and another resistor are added.
3) The 555 will be zapped and destroyed unless a diode is parallel with the relay coil.
4) The timing RC parts are missing in your circuit.
5) The 555 needs a power supply bypass capacitor.

As usual with ebay, the ad for the dw44 ne555 4pin timer module has absolutely no details except that it is "unbranded" (made in somebody's basement?).
 

MisterBill2

Joined Jan 23, 2018
5,186
Instead of guessing about a 555, why not look at its datasheet?

1) The trigger input pin2 needs a pullup resistor.
2) The timer will not time out if the switch remains turned on unless a capacitor and another resistor are added.
3) The 555 will be zapped and destroyed unless a diode is parallel with the relay coil.
4) The timing RC parts are missing in your circuit.
5) The 555 needs a power supply bypass capacitor.

As usual with ebay, the ad for the dw44 ne555 4pin timer module has absolutely no details except that it is "unbranded" (made in somebody's basement?).
The thing is a commercially produced product, perhaps not every component is shown.
 
EDIT. I confused this thread with another thread that uses a 3.6V battery to power a wireless keyboard. The user wants a bright blinking LED to occur when the Caps Lock key is active.
 
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