How to design a Transfer pump on/off circuit

Thread Starter

ralphspa

Joined Sep 12, 2016
14
I have a 12 volt oil transfer pump that a computer controls on/off. It transfers oil from main tank on boat to remote tank on outboard motor.
remote tank on motor has low/full level pair of switches that send a ground signal to computer depending on oil level. i would like to design an electronic circuit that will trigger pump to come on when low level switch grounds out and keep pump on until full level switch tell curcuit to turn pump back off.
I am unable to come up with an idea that will do this.
Any help would be appreciated
Thanks in advance
Ralph
 

R!f@@

Joined Apr 2, 2009
9,919
Welcome to AAC
It is easy.
Need some info though.
1. Operating Power of pump and available battery voltage.
2. What kinda limit sensors are used to sense empty and full conditions.
3. Do you have excess to these sensors wire terminals, if not do you plan on to install sensors.
And any other info you have will help.
 

Thread Starter

ralphspa

Joined Sep 12, 2016
14
Welcome to AAC
It is easy.
Need some info though.
1. Operating Power of pump and available battery voltage.
2. What kinda limit sensors are used to sense empty and full conditions.
3. Do you have excess to these sensors wire terminals, if not do you plan on to install sensors.
And any other info you have will help.
So I finally have some info needed.
Pump only draws 1 amp at 12 volts dc.
I have sensors accessible. Low level sensor pulses a ground when level low. A second pulses ground when full.
I'm not sure what kind of sensors they are tho. I can't seem to find info on that.
Any help would be appreciated.
Thanks
Ralph
 

crutschow

Joined Mar 14, 2008
34,838
A RS latch circuit driving a MOSFET should do the job.

Since you didn't post where you live I don't know what electronic parts suppliers you have ready access to. :confused:
 

R!f@@

Joined Apr 2, 2009
9,919
@crutschow suggested a simple method.
Since I can program simple code I would use a small micro (PIC) to do the job.
If you can program I can write you a little code for the Job
 

R!f@@

Joined Apr 2, 2009
9,919
By the way what is the voltage at the sensor output when the sensor in not active?
That is when sensor is not grounded or not it limit.
And I believe the system is a 12VDC one.
 

crutschow

Joined Mar 14, 2008
34,838
Below is he LTspice simulation of a circuit that I think does what you want.
The simulation shows the motor current for the Full and MT (Empty) switch operation.

I picked a common N-MOSFET to drive the motor, but any N-MOSFET with a voltage rating of ≥50V and an ON resistance of <0.5Ω should work.

The CD4011B is a CMOS NAND gate configured as a latch (4 gates in one package). The actual part number may contain some additional letters depending upon the manufacturer.
Note that you need to connect pin 14 of the IC to V+ and pin 7, as well as all unused inputs (not outputs) to ground.

R_Motor simulates the motor load and is not part of the built circuit.
D1 absorbs any motor transient voltages to protect the MOSFET.

upload_2016-11-2_15-47-42.png
 

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Thread Starter

ralphspa

Joined Sep 12, 2016
14
Below is he LTspice simulation of a circuit that I think does what you want.
The simulation shows the motor current for the Full and MT (Empty) switch operation.

I picked a common N-MOSFET to drive the motor, but any N-MOSFET with a voltage rating of ≥50V and an ON resistance of <0.5Ω should work.

The CD4011B is a CMOS NAND gate configured as a latch (4 gates in one package). The actual part number may contain some additional letters depending upon the manufacturer.
Note that you need to connect pin 14 of the IC to V+ and pin 7, as well as all unused inputs (not outputs) to ground.

R_Motor simulates the motor load and is not part of the built circuit.
D1 absorbs any motor transient voltages to protect the MOSFET.

View attachment 114664

Unfortunately I have knowledge of programming whatsoever. I only have automotive electrical experience and some basic electronics experience. I could build a circuit on a breadboard if I have a diagram and parts list tho.
 

crutschow

Joined Mar 14, 2008
34,838
Unfortunately I have knowledge of programming whatsoever. I only have automotive electrical experience and some basic electronics experience. I could build a circuit on a breadboard if I have a diagram and parts list tho.
My circuit requires no programming (why did you think it does).
It operates as shown, nothing else required.
Where would you buy the parts (Digikey, Mouser, Jameco...)?
Can you wire it following the schematic I posted?
 
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AnalogKid

Joined Aug 1, 2013
11,196
First pass at an alternate solution.

The ULN2003 has seven individual small power darlington transistors, with a common ground and a transient protection diode on each output. Each one is rated for 50 V and 0.5 A. It makes a great logic device for rugged environments, with each section acting as a high voltage open collector inverter. The small schematic in the corner shows the internal connections of each section. Two sections back-to-back form a flipflop, and five sections in parallel form the output motor driver. One chip, 2 resistors, no capacitors.

ak
Transfer-Pump-1-c.gif
 

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