Re: Mercedes fan upgrade
[Re: DaveRS23]
#838250
11/12/10 10:28 PM
11/12/10 10:28 PM
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Joined: Sep 2009
Posts: 1,805 ky hills
thehemikid
top fuel
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ky hills
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Quote:
WOW!!! I was just hoping to get a fan controller here, but I am getting an education to boot. Keep up the brain storming guys.
...Dave are you still looking/leaning towards variable speed or high & low by temp switch. ...
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Re: Mercedes fan upgrade
[Re: thehemikid]
#838251
11/13/10 02:06 AM
11/13/10 02:06 AM
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Joined: Oct 2007
Posts: 3,895 Oregon
hooziewhatsit
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Alrighty, I first tested by giving the trigger wire a variable voltage. It wouldn't turn on until I hit right near the battery voltage (12.7ish on this one). It didn't turn off again until I hit about 9.5v while slowly decreasing the voltage on the trigger wire. I didn't hear any difference in the fan speed between giving the trigger 12.3v or 9.5v. It was the same thing when I fed that voltage through the controller; with an 8v PWM it did not come on. With a 12v PWM, I couldn't hear a difference in speed between a 95% and 85% PWM. Sooooo, it appears that the fan is on/off only. I guess that makes the controller easier. Although with an HHR type fan, if there isn't a fancy controller onboard, I could switch the main current with a PWM to control its speed
If you ever find yourself in a fair fight, your tactics suck.
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Re: Mercedes fan upgrade
[Re: DennisH ]
#838253
11/13/10 02:09 PM
11/13/10 02:09 PM
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Joined: Jan 2003
Posts: 28,068 Irving, TX
feets
Senior Management
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Senior Management
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Posts: 28,068
Irving, TX
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Thanks, Dennis. That whole points and condenser thing worked out well too, didn't it? Now please go stand in the corner for sticking your nose where it doesn't belong. Dave, can you fire up the fan and let it run until the battery voltage will no longer support it? If the controller will run the fan for a long time without letting the smoke out then I believe your job is done. It makes for a cheap controller too. Adding variable speeds and other fun stuff is simply icing on the cake. I know the Mercedes fans fire up on a high speed then drop to a lower speed. I see and hear that happen in the shop all day long. Maybe MB drops the voltage after the fan hits it's top speed. Feel free to explore that if you like. I still would like to know if that 4th line is simply a feedback for the fan motor tachometer or if that is used for other purposes. Is it possible to dig into that when you have time? You can play with the HHR fan beside the MB fan and find out for yourself that it doesn't come close to moving the same air. The MB fan is also a better fit.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
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Re: Mercedes fan upgrade
[Re: feets]
#838254
11/13/10 10:51 PM
11/13/10 10:51 PM
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Joined: Oct 2007
Posts: 3,895 Oregon
hooziewhatsit
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Well, it ran for 22 minutes, until the voltage on the battery dropped to 10.2ish. 90% of that is about the 9.5v I observed earlier where it turned off. After a couple minutes for the battery to temporarily recover it started right back up (albeit with the voltage dropping quickly).
I was going to do some more research on the controller itself, and then try some different frequencies and see if I can make anything work.
Otherwise, it looks like the controller will be just be an on/off deal, driving the fan at 90%.
If you ever find yourself in a fair fight, your tactics suck.
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Re: Mercedes fan upgrade
[Re: hooziewhatsit]
#838255
11/13/10 10:54 PM
11/13/10 10:54 PM
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Joined: Jan 2003
Posts: 28,068 Irving, TX
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That's good enough for most folks. Some of us (read: Andrewh, me, and other EFI guys) would keep digging for more.
Making it on/off at a user adjustable temperature setting would make for an easily built and cheap controller.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
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Re: Mercedes fan upgrade
[Re: thehemikid]
#838259
11/16/10 03:08 AM
11/16/10 03:08 AM
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Joined: Oct 2007
Posts: 3,895 Oregon
hooziewhatsit
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I've tried drive frequencies from 30Hz, to 22kHz. At the higher frequencies, it still runs with a 10% PWM, but the fan speed doesn't change from the max. Without getting a mercedes on my Oscope, or getting documentation outlining how to control the fan, or even a wiring diagram, it looks like we'll be stuck with on/off However, since it will have a microcontroller in it, if I figure it out eventually, you can just send it back to me, I'll update the code, and you'll have variable speed Edit: I just shoved some wire into the plug to go to the 4th terminal. On the oscilloscope, it just goes high (12v) the entire time the fan is running. Usually, a circuit like this would have a resistor pulling it to 12v, then a switch to pull it to ground for each rotation. I'm not seeing anything like that.
Last edited by hooziewhatsit; 11/16/10 03:22 AM.
If you ever find yourself in a fair fight, your tactics suck.
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Re: Mercedes fan upgrade
[Re: Bens_Coronets]
#838262
11/18/10 02:16 AM
11/18/10 02:16 AM
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Joined: Oct 2007
Posts: 3,895 Oregon
hooziewhatsit
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Yea, the fan has the blades installed. It's also strapped to the old radiator out of my truck, so it has to pull air through that as well. At this point, I just need to do the circuit board layout and have those made (will take a couple weeks to turn around), then assemble, test, and ship And they'll be re-programmable on my end, so if we get variable speed working, they can be sent back for an upgrade. The fan itself is 600w. To put a resistor inline, it would have to burn off 300w in heat To make a power converter, it would also have to support about 300w, which is quite a bit. Since MB has variable speeds, I know it's possible; I just haven't figured out how (yet). At this point I'm contemplating only having one knob to select a target temperature. It will likely turn on a few degrees above that, and turn off a few below it. Thoughts?
If you ever find yourself in a fair fight, your tactics suck.
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Re: Mercedes fan upgrade
[Re: hooziewhatsit]
#838263
11/18/10 09:10 AM
11/18/10 09:10 AM
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Joined: Nov 2004
Posts: 7,274 s.w.fl
bonefish
OP
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Quote:
Yea, the fan has the blades installed. It's also strapped to the old radiator out of my truck, so it has to pull air through that as well.
At this point, I just need to do the circuit board layout and have those made (will take a couple weeks to turn around), then assemble, test, and ship
And they'll be re-programmable on my end, so if we get variable speed working, they can be sent back for an upgrade.
The fan itself is 600w. To put a resistor inline, it would have to burn off 300w in heat To make a power converter, it would also have to support about 300w, which is quite a bit. Since MB has variable speeds, I know it's possible; I just haven't figured out how (yet).
At this point I'm contemplating only having one knob to select a target temperature. It will likely turn on a few degrees above that, and turn off a few below it. Thoughts?
keep up the good work
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Re: Mercedes fan upgrade
[Re: Andrewh]
#838266
11/18/10 04:45 PM
11/18/10 04:45 PM
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Joined: Oct 2007
Posts: 3,895 Oregon
hooziewhatsit
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Quote:
few things. I never saw a report on a continous test with something charging the system to show 40 amps to the fan.
can you send the proto type instead of getting boards made? would rather check that out before you outlay money.
Yea, I can send the prototype first. I'll have to wrap it up since all the pins on the bottom are exposed. The board is roughly 4"x5" (final board will be much smaller). I also need to port the code to the cheaper microcontroller, so sending the prototype will give me time to do that.
Andrew, you're still planning on using an on/off relay to trigger it, correct?
The wider temp spread is a good idea.
When I had it running just off the battery, it should have been pulling its 40A. The battery just didn't last long enough for a proper test.
My battery charger is only good for 10A. I think I can kludge up a way run it off of the truck while it's idling (Then I'll see if my '70s alt can keep up with it , and it just started snowing, and I don't have a garage )
Weird side note: last night I was testing different drive frequencies, and found one frequency, with a specific PWM value, that would make the fan turn on for a second, then turn off. Before it stopped spinning it turned on again for a second, etc. I did quite a bit of testing around those frequencies, but didn't find anything useful
If you ever find yourself in a fair fight, your tactics suck.
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Re: Mercedes fan upgrade
[Re: Andrewh]
#838268
11/18/10 05:23 PM
11/18/10 05:23 PM
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Joined: Oct 2007
Posts: 3,895 Oregon
hooziewhatsit
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Ok, I think I know how to make it work on your system with a minimal amount of changes. It'll be easier to draw a picture. (it'll involve moving one wire to make the relay switch ground, rather than 12v, to my controller).
If you ever find yourself in a fair fight, your tactics suck.
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