Dc circuit help

MisterBill2

Joined Jan 23, 2018
5,186
I have increased and decreased the time and it does work as it should but only when I touch Vi to -12/GND the motor will operate for different amount of time depending on how many turns on the adjustment screw. The push button I am using is a NO when not pushed and closed when I push verified by multi meter
OK, so it seems now that what remains is getting the module to work with the sensor module output. The problem was not where everybody was looking, which explains why it was not found.
I think that you stated that the sensor module output is low when there is no water detected and goes high when it is detected. Thus the logic sense is reversed. A simple single NPN transistor can provide that logic sense reversal. BUT we will need to know just what the signal out of that sensor does.
 
In the first post he said, "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".

He was asked, "Without power, what is the resistance between Vi and pin 2 on the 555?" Then in post #62 he said, "47k between the two". But a 555 might not trigger from the water sensor in series with the with the 47k because Vi is +0.4 from the water sensor (it has some series output resistance) but Vi works fine when it is 0V.

I think the project will work fine if the 47k resistor is shorted.
 

ericgibbs

Joined Jan 29, 2010
9,537
hi agu,
I did ask him in post #63, what is the voltage on 555 pin #2, just in case the designer' has tied it to Vcc. in series with another resistor.[ still waiting his reply]
If it is not to Vcc, then as you say, short it out and use the 2 off, 10k resistors and 10n as per an earlier post.

E
 

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
hi agu,
I did ask him in post #63, what is the voltage on 555 pin #2, just in case the designer' has tied it to Vcc. in series with another resistor.[ still waiting his reply]
If it is not to Vcc, then as you say, short it out and use the 2 off, 10k resistors and 10n as per an earlier post.

E
will send that info when I get home tonight
 
Since the 47k resistor in series with pin2 of the 555 is messing up the pin2 low voltage then measure the pin2 voltage (not the input voltage that you said was 0.4V) when the sensor voltage is low.
 

MisterBill2

Joined Jan 23, 2018
5,186
There is your problem. Pin 2 of the 555 is shorted to +5V or has a very low value resistor to +5V.
The 47k input resistor makes it worse.
OK, now that a condition has been detected it may be time for a very strong magnifier to examine the module traces for solder bridges. BUT I thought that in a very recent post correct operation of the timer module had been verified. That is the comment that I responded to in post #63. So if the timer module triggers and delivers the correct operation then probably the next thing would be to evaluate the module producing the signal to see why it is not triggering the timer.
 

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
OK, now that a condition has been detected it may be time for a very strong magnifier to examine the module traces for solder bridges. BUT I thought that in a very recent post correct operation of the timer module had been verified. That is the comment that I responded to in post #63. So if the timer module triggers and delivers the correct operation then probably the next thing would be to evaluate the module producing the signal to see why it is not triggering the timer.
But even with a push button in place of optical sensor to trigger timer, the timer still did not trigger when voltage was low or 0 with the push button. I believe the way the Dw44 is built it needs to short out/GND the trig to operate, that’s just a guess not sure if that is correct or not but out of the two different DW44 that I have that is the only way I can get either of them to operate.
 

ericgibbs

Joined Jan 29, 2010
9,537
hi EZ,
I know it sounds a little drastic, but I would de-solder/remove the 555.
Meter the 555 PCB pads and determine the actual circuit and how the external pins are connected. [draw out the circuit]
It is possible that the 555 maybe faulty.

Is it also possible for you to test the 555 on a simple test board.???

You have nothing to lose in doing this dismantle as the modules do not work in their present condition.

E
 

MisterBill2

Joined Jan 23, 2018
5,186
But even with a push button in place of optical sensor to trigger timer, the timer still did not trigger when voltage was low or 0 with the push button. I believe the way the Dw44 is built it needs to short out/GND the trig to operate, that’s just a guess not sure if that is correct or not but out of the two different DW44 that I have that is the only way I can get either of them to operate.
WAIT A MINUTE NOW!! how can this be? What is the difference between using the pushbutton, which is connected between the Vi terminal and the Gnd terminal. Of course, I have been guessing that the Gnd termianl is connected to the negative side of the 12 volt supply. So now I ask why the timer appears to function correctly when the connection from the Vi terminal is made with a wire but not when it is made with the pushbutton. Clearly there is some detail that has not been provided to us. Clearly a more complete explanation of just what the connections really are will be a good start.
 

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
WAIT A MINUTE NOW!! how can this be? What is the difference between using the pushbutton, which is connected between the Vi terminal and the Gnd terminal. Of course, I have been guessing that the Gnd termianl is connected to the negative side of the 12 volt supply. So now I ask why the timer appears to function correctly when the connection from the Vi terminal is made with a wire but not when it is made with the pushbutton. Clearly there is some detail that has not been provided to us. Clearly a more complete explanation of just what the connections really are will be a good start.
Sorry I am getting all my responses mixed up
Ok it will work if push button is hooked up to to negative/GND of power supply.
I was referring to post #44 with the push button not working hooked up that way.
 

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
My guess is that the optical output is not a Negative/GND signal when in the water it’s still a positive hens the .4v still on when closed and the 5v when open. I would need to supply a negative/GND to the input of the DW44 or Vi to trigger timer.
 

MisterBill2

Joined Jan 23, 2018
5,186
I already suggested using a CMOS inverter IC to both provide the logic inversion AND provide an increased pull-down so as to trigger the timer. That IC costs less than a dollar and it can be used with either a 5 volt supply or a 12 volt supply. But if you need a device in a module with terminals it will take a bit more effort.
I believe that the original post did state that the sensor module held a high output that went to zero when water was detected.
 

Thread Starter

ElctronicZombie

Joined Jan 19, 2020
43
I already suggested using a CMOS inverter IC to both provide the logic inversion AND provide an increased pull-down so as to trigger the timer. That IC costs less than a dollar and it can be used with either a 5 volt supply or a 12 volt supply. But if you need a device in a module with terminals it will take a bit more effort.
I believe that the original post did state that the sensor module held a high output that went to zero when water was detected.
Yes sensor output is 5v when open/dry and .4v when closed/wet reading with a multimeter
 
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