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Engine-Off-Coast
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Discussion Starter #1
I know this is the wrong category but I figured this is where all the technical minds are most likely to see this post.

I am working on a 2005 Honda Accord Hybrid. I want to install a grid charger harness. The fan appears to be PWM because it has 4 wires. Ideally I would just hook up a +12V and a ground to it and it would run full blast, because that is very simple. But I suspect that is not possible.

I have arduinos, diodes, and transistors at my disposal. I know the Arduino has PWM output on the analog pins but that's only 5v. Could I use that to turn on and off a transistor that allows 12v to flow, or am I fundamentally misunderstanding PWM?

Again simplest solution is best. I just want the fan to run at any speed fast slow whatever. Here is a photo of the connector.

84599
 

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PC fans - Yellow is usually +12v, Black is usually Ground.

If it doesn't run at full blast have a look at this:


The connector on your fan is not following the standard color code, but the red and white wires should be tach and PWM/contol. I don't know which is which on your fan.

The tach is an input to the PC to let the PC know what speed it's running at. The PWM/control is a 5v logic level output from the PC to control the fan's speed.

DON'T HOOK THE RED OR WHITE WIRES OF YOUR FAN TO 12V.
 

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Discussion Starter #4
Okay so if I absolutely need to use a 5v logic output I could get an Arduino to do that.

I guess my main question about PWM is like, without a PWM signal, will the fan spin? And my immediate follow-up to that is, if not, will I blow the fan by trying to give it +12V?

I can try probing the two big leads when the car is on but the fan is NOT running to see if the 12V is hot at all times. If it is then we know that the fan won't run without the PWM signal. I wish I had the electrical troubleshooting manual for the HAH1 but I don't.

My grid charger uses a Meanwell RS-25-12 for 12V supply. It says 25 watts 2.1 amps. I suspect this may not be enough depending on the fan power. I might have access to a 12V laptop supply if this is the case.
 

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It might be the same/similiar as the HCH2 fan.

My manual for that says.

Red. 12v+
Black. Gnd
Purple. Fan Speed Feedback Output
Light Blue. Fan PWM drive Input (Logic level drive) (Try connecting this to gnd or +5V)
 

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Hi Natalya,

Google "logic level FET". These are FETs that can be driven directly from the output of an Arduino. If that pin is a PWM pin, easy peasy. WeiMeet RFP30N06LE 30A 60V N-Channel Power Mosfet TO-220 ESD Rated for Arduino(10 Pieces):Amazon:Industrial & Scientific

Also, consider one of these toy oscilloscopes. They can help you quickly discern signals like those being sent to the fan, sent from an EGR valve, etc. Mine takes 9V; you can power it from a wall wart but that's no fun. I have mine velcroed to a cell phone charging battery that can also output 9V.


A fun project would be to 3D print a new rear cover for that scope into which a battery could be put. But for the additional cost in parts there is probably a decent scope out there with battery operation.

Best!
 

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Also - PWM is probably used so that they can keep the noise down and drive at a lower speed if it isn't monster hot. You probably can just connect directly to 12V to see how much current it draws. I like to use a voltmeter that has a clamp-on DC ammeter (watch out if comparing them, many of them only do AC). Or you can use one of these to measure current with an Arduino, but not as easy as just clamping a meter around a wire: FTCBlock 3pcs Current Sensor ACS712 5A 20A 30A Range Analogue AC/DC for Arduino Ras PI:Amazon:Industrial & Scientific Note that this module comes with a 5A, 20A, or 30A max current (ie, if you think the fan is only pulling amps, stick with 5A).
 

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Discussion Starter #10
Hooking the fan to a 2A 12V supply didn't activate it. Will have to go the PWM route. I've started a Mouser shopping cart with the mosfet you mentioned. But I'm not sure what else I'll need. I may need a higher-amperage 12v supply as well.

I don't have a way to get the Accord to activate the fan so I can't measure the fan current.
 

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2 amps at 12vdc should have made it move. Which wires did you apply the 12v to? If you're concerned about the power supply you could always jump it to a car battery.
 

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Looking back at Peter's post, I think I misunderstood the fan operation. I read too fast, and the original picture did not load before I scrolled past it due to my fantastic internet connection.

I thought the fan speed was controlled by pulse width modulating the power to the fan, thus the logic level FET suggestion. These are handy to have around, but sounds like it is not needed (or maybe it is)

It does sound like, based on Peter's suggestion, that you apply 12V and on the PWM line, a PWM signal (logic level = an Arduino should be able to provide it as you have surmised) to drive it. (Gotta wonder, if you took it apart, if that that input goes into a logic level FET?)

Peter suggested holding that input to 5V or ground, I think which would correspond to 100% or 0% duty cycle, and see if it turns on.

But personally, I would like to know for sure what the operating voltage is before frying something. My device of choice is an oscilloscope. You can find a cheap one on Ebay used, or you can get one on Amazon. Last year I bought this tiny one which works pretty well: Oscilloscope Kit, KKmoon KKmoon 2.4" TFT Digital Oscilloscope Kit with Power Supply and BNC-Clip Cable Probe DS0150 (Assembled Finished Machine):Amazon:Home Improvement It cost a little less then, and didn't come with the probe (just the BNC cable with clip leads on the other end.)

For a little more money you could certainly do better, but it fit the niche I needed at the time.
 

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Yes use a 1k resistor in line with the pwm line when testing in case all is not as it seems......
Measure the current as well into the line as well.
 
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