Bypass ECU :: Radiator Fan Control Switch

Ian Rogers · Oct 19, 2016

pradoartz said:
What do you do? Are you an electrical & electronic engineer ?

I think we all are here!!

I have put this circuit into Proteus... Works as expected!

spec · Oct 19, 2016

pradoartz said:
N1A, N1B ARE DIFFERENT ?

Yes, N1A and N1B are two independent comparators in one eight-pin plastic case. Only N1A is used in the MFC. N1B is not used, but its + and - inputs must be connected as shown in the schematic so that N1B output is in a defined state, and N1B does not misbehave.

spec

pradoartz · Oct 19, 2016

Ian Rogers said:
I think we all are here!!

I have put this circuit into Proteus... Works as expected!

Please Can u send me the Proteus template file for this circuit. My mail I'd is pradoartz@gmail.com

pradoartz · Oct 19, 2016

spec said:
Yes, N1A and N1B are two independent comparators in one eight- pin plastic case. Only N1A is used in the MFC. N1B is not used but its + and - inputs must be connected as shown in the schematic so that N1B output is in a defined state and N1B does not misbehave.

spec

Eight-pin plastic case? What is that. Can u show me an image. Already said u I am dumb in electronics. Lol.. I am a computer science engineer.

spec · Oct 19, 2016

Here is a drawing of the 8 pin plastic case that contains N1A and N1B. The pin numbers correspond to the pin numbers shown on the schematic. The drawing is from the LM393 dual comparator integrated circuit datasheet: https://www.ti.com/lit/ds/symlink/lm2903-n.pdf

When you build the circuit it would be best to put the LM393 in an 8 pin turn-pin IC socket. You first wire the socket into your circuit and then plug the actual LM393 integrated circuit into the socket. Note that you should only use a turn-pin socket for maximum reliability.

Diver300 · Oct 19, 2016

A couple of the circuits here show a diode in parallel with the relay. That can slow down the opening of the relay. It is better to put a resistor in parallel with the relay coil, and chose a value about 10 times the coil resistance. That will limit the surge voltage to around 10 times the supply voltage, so easy enough to manage with a transistor of a reasonable voltage rating.

If you use a diode, and the contacts open slowly, with a big load like a fan, you can easily burn the contacts.

spec · Oct 19, 2016

Thanks Diver.

I have some more work to do on the fan snubber: one reason why I was biased towards using the existing motorcycle relay, especially as I have no data on the fan characteristics.

spec

PS: don't worry about this aspect pradoratz- it is not a show stopper.

robertmaks · Oct 19, 2016

A good choice, although a bit more work would be to construct a simple Arduino circuit with a mostfet for the fan and a voltage divider on the sensoe going into an analog input, a quick pwm tutorial with a pot to control the pwm of an led can be adapted to your needs with a caouple changes in the Arduino sketch(some numbers). That's how I would prefer to do it but analog is quite good way to do it also.

spec · Oct 19, 2016

Hi Robert,

Welcome to ETO. I see you are from the States, which one. If you put it next to 'Location' on your user page it will show in the panel on the left of your posts.

robertmaks said:
A good choice, although a bit more work would be to construct a simple Arduino circuit with a mostfet for the fan and a voltage divider on the sensoe going into an analog input, a quick pwm tutorial with a pot to control the pwm of an led can be adapted to your needs with a couple changes in the Arduino sketch(some numbers). That's how I would prefer to do it but analog is quite good way to do it also.

Theoretically an interesting approach, but there are a number of issues:

(1) Why use Pulse Width Modulation (PWM)? The fan is either on or off; fan speed control is not required.
(2) The OP has no experience of electronics, let alone microcontrollers
(3) PWM is a higher risk, especially as we do not know the characteristics of the fan.
(4) Electromagnet compatibility (EMC) could be a problem
(5) Snubbing would be more critical
(6) The MOSFET would be more vulnerable, more critical, and more expensive
(7) You would need an extended temperature range microcontroller
(8) The microcontroller would need a program, implying an integrated development environment (IDE) and host
(9) The microcontroller would require a stabilized supply line (5V or 3.3V)
(10) By definition, the reliability would be less
(11) The cost would be higher and component availability would be worse.
(12) Susceptibility to electrostatic discharge (ESD) would be worse.
(13) The MFC would be more susceptible to moisture
(14) The relay provides isolation between the blood and thunder of the fan circuit and the decoupled supply line for the Schmitt trigger. A MOSFET controlling the fan directly does not do this.

By the way, I did consider driving the fan directly with a MOSFET, rather than a relay, but decided against it on the grounds of risk and reliability: switching fans with automotive relays is universal and well proven.

spec

pradoartz · Oct 20, 2016

spec said:
POST ISSUE 17 of 2016_10_20

(6) R6 defines the hysteresis of the Schmidt trigger (N1A). With the value shown the hysteresis will be 5 Deg C. Thus, if the fan turn-on temperature were set to 80 deg C, the fan would turn on at 80 Deg C and would not turn off until the water temperature had dropped to 75 Deg C.

got all spares ordered.

pradoartz · Oct 20, 2016

spec said:
POST ISSUE 17 of 2016_10_20

DATA SHEETS & SOURCES
(1) Comparator dual: LM393: https://www.ti.com/lit/ds/symlink/lm2903-n.pdf
(2) power transistor: TIP 42x: https://www.onsemi.com/pub_link/Collateral/TIP41A-D.PDF
(3) Relay: Single pole, single throw, automotive type. Coil, 12V, 80 Ohms. Contacts, 30A minimum
(4) Potentiometer: 50K, pre-set, multi-turn
(5) Diode: 1N4002 to 1N4007.
https://www.vishay.com/docs/88503/1n4001.pdf
(6) Diode: VSB1545_M3, 25V min, 10A min:
**broken link removed**
https://www.digikey.co.uk/product-d...on/VSB1545-M3-54/VSB1545-M3-54GICT-ND/4810661
(7) Capacitor: aluminum electrolytic, high ripple current, high temperature, 470uF, 25V minimum
(8) Capacitor: disk ceramic, 100nF, 25V minimum, X7R dielectric (not surface mount)
(9) Resistor: all resistors, unless otherwise stated, are metal film, or metal oxide (not carbon), through hole (not surface mount), 250mW minimum, 5% or better
(10) Fuse: FS1 is a 10A automotive type (as I do not know the characteristics of the fan, 10A is only an estimate)

Can u please check the components i choose to order online, Will order it after your confirmation.

spec · Oct 20, 2016

Hi pradoartz,

Some of the components on your list are not quite correct. If you send a link to the supplier you wish to use I will see if I can do a list for you.

spec

pradoartz · Oct 20, 2016

spec said:
Hi pradoartz,

Some of the components on your list are not quite correct. If you send a link to the supplier you wish to use I will see if I can do a list for you.

spec

in.element14.com/
**broken link removed**components.com/

robertmaks · Oct 20, 2016

spec said:
Hi Robert,

Welcome to ETO. I see you are from the States, which one. If you put it next to 'Location' on your user page it will show in the panel on the left of your posts.

Theoretically an interesting approach, but there are a number of issues:

(1) Why use Pulse Width Modulation (PWM)? The fan is either on or off; fan speed control is not required.
(2) The OP has no experience of electronics, let alone microcontrollers
(3) PWM is a higher risk, especially as we do not know the characteristics of the fan.
(4) Electromagnet compatibility (EMC) could be a problem
(5) Snubbing would be more critical
(6) The MOSFET would be more vulnerable, more critical, and more expensive
(7) You would need an extended temperature range microcontroller
(8) The microcontroller would need a program, implying an integrated development environment (IDE) and host
(9) The microcontroller would require a stabilized supply line (5V or 3.3V)
(10) By definition, the reliability would be less
(11) The cost would be higher and component availability would be worse.
(12) Susceptibility to electrostatic discharge (ESD) would be worse.
(13) The MFC would be more susceptible to moisture
(14) The relay provides isolation between the blood and thunder of the fan circuit and the decoupled supply line for the Schmitt trigger. A MOSFET controlling the fan directly does not do this.

By the way, I did consider driving the fan directly with a MOSFET, rather than a relay, but decided against it on the grounds of risk and reliability: switching fans with automotive relays is universal and well proven.

spec

Live life to the fullest, really your overthinking this. PWM is more contolled and when I started electronics I jumped right into many things like Arduino without any prior knowledge and learned a lot, so let him give it a try and if it does not work (the PWM) just change a few lines and bob's your uncle. It can just switch on or off.

spec · Oct 21, 2016

Hi Robert,

robertmaks said:
Live life to the fullest

This is a technical thread. ETO 'Member's Lounge' is for philosophy.

robertmaks said:
really your overthinking this.

It is called good design. To ignore the points I made is bad design.

robertmaks said:
PWM is more contolled

?

robertmaks said:
when I started electronics I jumped right into many things like Arduino without any prior knowledge and learned a lot, so let him give it a try and if it does not work (the PWM) just change a few lines and bob's your uncle. It can just switch on or off.

You are making circular arguments and not dealing with all of the aspects of this application, including the OPs position. Let me repeat again PWM is not required.

I am sure you mean well, but please be specific and give qualified answers.

I would be interested to see your alternative circuit for this application.

spec

pradoartz · Oct 21, 2016

pradoartz said:
in.element14.com/
**broken link removed**components.com/

Hi bro, did u find the components from the suppliers i sent?

spec · Oct 21, 2016

pradoartz said:
Hi bro, did u find the components from the suppliers i sent?

Working on it- will post list soon.

spec

pradoartz · Oct 21, 2016

Today i got this image.

pradoartz · Oct 21, 2016

robertmaks said:
Live life to the fullest, really your overthinking this. PWM is more contolled and when I started electronics I jumped right into many things like Arduino without any prior knowledge and learned a lot, so let him give it a try and if it does not work (the PWM) just change a few lines and bob's your uncle. It can just switch on or off.

Hi friend,
Can u make an alternative circuit for this application using arduino?? i don't have any experience in programming arduino. So i asked brother spec to design me an circuit based. Anyways i am going with spec, but if u can do it in arduino, it will be useful in future for many peoples.

I think this links below can help you understanding the query.
https://priuschat.com/threads/arduino-automatic-coolant-temp-hack-for-better-mpgs.90418/

**broken link removed**

Thanks

spec · Oct 21, 2016

Hi pragoartz,

As promisede the bill of materials (BOM) (parts list) for the circuit of post #26 is attached to the end of post #26.

I tried to find most components on electron.com because they are cheaper. Other components are from Element14.

That will mean two orders, but if you would like to order all parts from one supplier I will revise the BOM to source all components from Element 14.

spec

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