This component has to exist...

[rcdavi3]

I have a limo business with an older limo that is experiencing electronic control problems. I could pay 1700 for a new control system, but the limo can only be registered in this city for another 2 years so I just don't see it being worth the investment. I am talented enough to completely create my own relay and switch based control system but I can't figure out the fan motors. The limo has five fans that the limo all runs at the same speed (H/M/L). I figure I can control one at a time with potentiometers or various value resistors on a three-position switch to achieve the same control but for only one motor. Is there a device that will allow me to say feed a variable reference signal, and have that device output the same voltage but be able to take the amperage of these motors. Each motor can pull up to about 15 amps. I figure for example feed a six-volt reference signal branched out to say five of this device (one dedicated to each motor for isolation purposes) and have that device duplicate that voltage from an input of 12-14 VDC.... Is this possible?

 

[Menticol]

If I understood right, you want a circuit to regulate the speed of various fans, using the same control signal for all of them, right?

In that case you need to google PWM fan controller.

This is an example for a small computer fan, but I guess it could be scaled up for your big 12V 15A fan motors
**broken link removed**

 

[alec_t]

Perhaps something like this? A pot provides continuous speed control from very slow to full, but could be replaced by switched resistors.
The contents of the dotted rectangle constitute one module; you will need 5 such modules for the 5 fans.

 

[rcdavi3]

Looking over the schematic, I understand most of it, but there are bit's that I just don't get... I can locate U1a-U1d and corresponding pins 1-6 and 8-13, however, there are two connections that seem to want to be connected to U1pin 14 and one that wants U1pin 7?

 

[Mickster]

Looking over the schematic, I understand most of it, but there are bit's that I just don't get... I can locate U1a-U1d and corresponding pins 1-6 and 8-13, however, there are two connections that seem to want to be connected to U1pin 14 and one that wants U1pin 7?

U1pin 14 is power supply.
U1pin 7 is ground.

Power supply is decoupled via 100n across supply pins

U1 is the IC.
CD4093 - QUAD 2-INPUT NAND SCHMITT TRIGGER
Datasheet:
https://www.alldatasheet.com/datasheet-pdf/pdf/26897/TI/CD4093.html

Regards.

 

[kinarfi]

Another method is to create a triangle wave and compare it to a dc voltage to get the PWM to drive the motor via a FET, Here's what I'm doing for a scooter that uses 24 volts, but the control part is 12 volt, take look and see if you think it will work for you.

 

[kinarfi]

If you haven't found a solution yet, speak up, but here's a link with a circuit that could be modified to fill your needs
https://www.electro-tech-online.com/custompdfs/2012/07/k166.pdf

 

[shokjok]

kinarfi, the zener diode feeding the MOSFET in your attachment is not identified. Should it be a rectifier?

 

[kinarfi]

MBRB2545CT Dual Schottky Barrier Rectifier, Forward Current 30A Vishay