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Timer circuit wont turn off V output

Hi all,
I have a simple 12v pump control that only reduces the output voltage from 13v to 12.4v and hence the pump continues to run. I have replaced the two main Mosfets and IC555. The resistors and caps all test within their specs.
Any ideas or help appreciated.
Ernie
Edit to add further info: This is a OEM control they sell as an option that plugs into the 12v pump. It allows you to turn the pump on or off with a main toggle switch. Its main feature is a potentiometer dial to adjust how long the pump is on or off. eg set at 1 the pump is off for ~ 18secs and on for ~4, at position 8max it is opposite - off for ~4secs then on for ~18 secs. However when off and the LED changes to RED from yellow, it is still outputting 12.45v and the pump keeps running.
 
Last edited:

davenn

Moderator
Hi Ernie,
welcome to EP :)

Hi all,
I have a simple 12v pump control that only reduces the output voltage from 13v to 12.4v and hence the pump continues to run. I have replaced the two main Mosfets and IC555. The resistors and caps all test within their specs.
Any ideas or help appreciated.
Ernie

well first off a schematic of your timer and maybe a photo or 2 of it so people can see if there are any problems

I'm assuming you built this timer?
Did it originally work and then stop,?
or did it never work from when you finished the construction ?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
My bet is that you have the MOSFET around the wrong way. Thus, when it is on, it is on; when it is off, conduction is via the body diode.
 
Hi Ernie,
welcome to EP :)



well first off a schematic of your timer and maybe a photo or 2 of it so people can see if there are any problems

I'm assuming you built this timer?
Did it originally work and then stop,?
or did it never work from when you finished the construction ?

Thanks for the reply.
No it is a OEM controller for a 12v pump sprayer. There are no visual clues and I have also replaced two of the 4 caps but to no avail. The fact that the voltage drops and the LED circuit switches as it should seems to show the switching side of things is servicable. The Mosfets seemed like the culprit but also no luck. It is like they switch but the gate to shut the voltage off doesn't seem to change much (other than the ~ 0.5v drop). I was expecting the resistors to be at fault but they test ok inspec with their rated colour bands. Ill try to get a decent pic.
 
If you purchased it somewhere, perhaps a link to the unit also?
Unfortunately they dont show any info relating to the Controller section and definitely no schematics. Just want to charge $1000+ to replace the whole controller. All the manuals and IPB pics relate to the sprayer - nothing on the remote on off controller.
 
Hi Ernie,
welcome to EP :)



well first off a schematic of your timer and maybe a photo or 2 of it so people can see if there are any problems

I'm assuming you built this timer?
Did it originally work and then stop,?
or did it never work from when you finished the construction ?
FYI I edited the original post to add further info.
 
Hi Ernie,
welcome to EP :)



well first off a schematic of your timer and maybe a photo or 2 of it so people can see if there are any problems

I'm assuming you built this timer?
Did it originally work and then stop,?
or did it never work from when you finished the construction ?
 

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If I measure V across the two resistors between the large mosfets, (pic 1) I get the 12.45v then drops to 1.35v. Indicating that this portion switches but voltage at the output is still full battery voltage 13.05v like it is shorted somehow.
 
Your pics need to be square on and high res and in focus if possible so people can make out details.
Quick drawing to hopefully better explain pic 3 of the back of the pcb with the components .
 

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If I measure V across the two resistors between the large mosfets, (pic 1) I get the 12.45v then drops to 1.35v. Indicating that this portion switches but voltage at the output is still full battery voltage 13.05v like it is shorted somehow.
Or held open to let full voltage through.

Components replaced so far: 2xmosfets , 557 transistor, ic555, 2x35v100 caps.
 
Last edited by a moderator:
Sir Ernie1979 . . . . .

" they . . .Just want to charge $1000+"

From what I am seeing of that unit, as being compared to a relative true worth . . . . I hope that those " ECCLESIASTICALLY accursed " . . . ." maternally copulating " . . . . " Sweet Ole Boys " have a 1000 units all tied up in their stock inventory and never sell a single unit, 'til hell freezes over. ! Damn carpetbaggers . . .


I am just making initial minimum changes a la schematic . . . ..
I notice that your +12 power supply buss travels across the very top and then drops down to power the 555 and later the 557 LED driver transistor and FINALLY your having it connected into the GATE ? ? ? ? ? of the IRF44. See if it is not being wired as I have changed it to, on the Source . Since Drain and the heat sink tab are being directly connected.

Looking at the whole assembly.. . . .
Am I correctly seeing the RED and BLACK stubbed and tinned wires as being the connections to the pump proper, that would terminate at the nearby YELLOW screw Euro connector.
Meanwhile, the extreme end of the boards 2 pin Euro connector is acccepting the 12VDC power in ?

Now back to the very slightly revised schema.. . . .
The 555's pin 3 feeds drive to the Z44 base via the RED DOT line path, along the way it drops off at the VIOLET DOT path with base drive for the 557 LED driver transistor. Also the BLUE dot path feeds to the gate of the STP FET, but with those 4-5 band resistors, 10 ohms seems WAY low, so see if you don't need to add a trailing zero or two.

Don't know what the STP does, but since I am NOT physically being able to see your "S/W" at top left corner. NOR its wiring GAUGE being used.
Somehow I want to think that the STP is being a power switch, being turned on, into conduction, by a minimally power / current rated "S/W" by establishing its gate drive. .

Pee Ess . . . . . I am experiencing an optical " collusion " . . . of seeing a double stacked STP. Surely that is a mirror polished tin plate on that foil heat sink rectangle, that the STP is screwed down to . . . . and casting a mirrored reflection..

***** Also tell me what the the Yellow / RED LED action light sequences are, under the different situations .********

First quick test would be to disconnect from battery and test the ohms reading from D-to S of the 44 and then the STP, with the RED and Black wires still being UN-connected..

Now I never have seen an IRF 44, with other than its heat sink tab showing, but the STP might be offered in the same exposed heat sink tab exposed, BUT ALSO in a polycarbonate case ( insulated) which only lets you make Drain connection to the center leaded terminal.
Use an exposed heat sink tab version and you would have to mica insulate the tab, or get an UNWANTED SHORT.

PSEUDO RE-REFERENCE . . . . . .


pnGPDyT.jpg


https://i.imgur.com/pnGPDyT.jpg

73's de Edd
.....................


Now, if people EVOLVED from apes, why are there still being apes around ?
 
Last edited:
Sir Ernie1979 . . . . .

" they . . .Just want to charge $1000+"

From what I am seeing of that unit, as being compared to a relative true worth . . . . I hope that those " ECCLESIASTICALLY accursed " . . . ." maternally copulating " . . . . " Sweet Ole Boys " have a 1000 units all tied up in their stock inventory and never sell a single unit, 'til hell freezes over. ! Damn carpetbaggers . . .


I am just making initial minimum changes a la schematic . . . ..
I notice that your +12 power supply buss travels across the very top and then drops down to power the 555 and later the 557 LED driver transistor and FINALLY your having it connected into the GATE ? ? ? ? ? of the IRF44. See if it is not being wired as I have changed it to, on the Source . Since Drain and the heat sink tab are being directly connected. Yes like my pic not yours.

Looking at the whole assembly.. . . .
Am I correctly seeing the RED and BLACK stubbed and tinned wires as being the connections to the pump proper, that would terminate at the nearby YELLOW screw Euro connector. Yes correct
Meanwhile, the extreme end of the boards 2 pin Euro connector is acccepting the 12VDC power in ? Yes

Now back to the very slightly revised schema.. . . .
The 555's pin 3 feeds drive to the Z44 base via the RED DOT line path, along the way it drops off at the VIOLET DOT path with base drive for the 557 LED driver transistor. Also the BLUE dot path feeds to the gate of the STP FET, but with those 4-5 band resistors, 10 ohms seems WAY low, so see if you don't need to add a trailing zero or two. I questioned this too - but it is definitely correct = 10 ohms and meter test reads 10 ohms. (Brown, blk, blk, gold. 100/10=10)

Don't know what the STP does, but since I am NOT physically being able to see your "S/W" at top left corner. NOR its wiring GAUGE being used. The big black toggle sw on/off is soldered to the pcb.
Somehow I want to think that the STP is being a power switch, being turned on, into conduction, by a minimally power / current rated "S/W" by establishing its gate drive. .

Pee Ess . . . . . I am experiencing an optical " collusion " . . . of seeing a double stacked STP. Surely that is a mirror polished tin plate on that foil heat sink rectangle, that the STP is screwed down to . . . . and casting a mirrored reflection.. Yep your not loosing it ;-)

***** Also tell me what the the Yellow / RED LED action light sequences are, under the different situations .******** When the light is Red = 12.45v, light yellow = 13.05v (my battery voltage), hence I believe when yellow it should cut off voltage inorder to stop the pump. With the mian toggle switch OFF, the lights continue to switch but there is 0V at the main output to the pump and hence pump turns off. With switch ON I get the above.

First quick test would be to disconnect from battery and test the ohms reading from D-to S of the 44 and then the STP, with the RED and Black wires still being UN-connected.. D-S of 44 = 6 Mohm, D-S of STP= Open ALSO, if i test voltage over the 10k and 4.7k resistors it switches from 12.45v to ~1.2v, which is how i expect it to be at the Main Voutput but it is 13.05v.

Now I never have seen an IRF 44, with other than its heat sink tab showing, but the STP might be offered in the same exposed heat sink tab exposed, BUT ALSO in a polycarbonate case ( insulated) which only lets you make Drain connection to the center leaded terminal.
Use an exposed heat sink tab version and you would have to mica insulate the tab, or get an UNWANTED SHORT.

PSEUDO RE-REFERENCE . . . . . .


pnGPDyT.jpg


https://i.imgur.com/pnGPDyT.jpg

73's de Edd
.....................


Now, if people EVOLVED from apes, why are there still being apes around ?
Thanks for the reply de Edd. Info above in your quote typed in BLUE to answer a couple of your questions.
 
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