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Topic Review (Newest First)
05-05-2013 04:23 PM
horsedad58 Freeskier,

Appreciate it. No rush on my part, whether it works or not I think it's going to just be fun playing with it. Good luck on both the studying and your finals..
05-05-2013 11:42 AM
freeskier I use sparkfun a lot, their warehouse is here in Boulder, which is 10 minutes from my house. If they have stuff in stock I usually just go pick it up.

Some other notes, I didn't look at the ATtiny85 data sheet in a lot of detail but I'm pretty sure those pin assignments will work. They are all I/O pins but only two of them are PWM.

The diode on the motor is a 1N4001.

I'll probably pick up the parts this week after finals. If I get anything now I'll just procrastinate studying...

If I add the mosfet driver I'll throw up another schematic. That will take a bit longer though because I actually have to do math. The driver has some circuit protection features so I would need to figure out some resistor and cap values to make that work.
05-05-2013 07:54 AM
horsedad58 Freeskier,

Awesome! I will be placing a parts order today. Gotta go find my proto-board. I have an old fan, old control panel so I can do some real world testing. I need to go read the lower speed voltages on the jeep too just to see what I need if i decide to do a fixed step version. (No other reason than I want to play.) I will probably just use a chunk of sheet alum for a heat sink.

I have never used sparkfun, I usually have gone to jameco. I assume that you've had good luck with sparkfun?

Also, thanks for sharing the schematic. I appreciate it and enjoy learning new stuff...
05-04-2013 10:41 PM
freeskier Here's a schematic I came up with.

Attachment 245163

Parts

- https://www.sparkfun.com/products/10213
- https://www.sparkfun.com/products/9378
- https://www.sparkfun.com/products/107

There's a pot in there, pull down resistor for the gate, and diode for motor "flyback". I'm also probably going to throw a mosfet driver in there because I'm not 100% convinced the controller's 5v can adequately control the mosfet's gate.

For a board layout I'd use board-to-wire molex connectors and add some heat sinks.

Driver

- http://cds.linear.com/docs/Datasheet/1155fa.pdf
05-03-2013 04:19 PM
horsedad58
Quote:
Originally Posted by freeskier View Post

The AVR controller is pretty cheap (3 bucks). I work at Colorado Space Grant on the RockSat-9 team, we are using AVR chips on custom PCBs so we have some AVR programmers laying around that should work. Also looks like the ATtiny 85 can also be programmed with an Arduino Uno.

Infinite speed would be cool, it would depend on how easily I could modify the stock switch with a potentiometer or something else. Otherwise just using the regular switch with 4 preset resistances would work.
Freeskier, i just looked at my old control panel (out of my 05) and the 4 position switch simply mounted to the back with 2 screws. The mounting area is flat and fabing a small alum plate to mount a long shaft pot would be simple.

Attachment 244650

Picture from the back.

Attachment 244651

Picture looking thru the panel. It even has a support brace for a long shaft.
05-03-2013 04:08 PM
horsedad58 Flyinhi4u, the box says TYC. That's all... Its probably Chinese but i ordered it thru amazon.com.

I have the old box because I saved the old fan in it to test my crude speed controllers on. I spins but clearly draws high current so I figure if a controller works with the old fan it will work with a new fan
05-03-2013 03:43 PM
freeskier https://www.sparkfun.com/products/9107

Looks like it can handle 21 amps with a heatsink. I think that might be enough to handle the blower motor. You'd still need something external though to step down the voltage for the controller and something to create the PWM signal.

I think something custom would still be better.
05-03-2013 03:34 PM
freeskier
Quote:
Originally Posted by horsedad58 View Post
Freeskier, you're headed down the same path i was going.... but you clearly understand what is needed. I, unfortunately, happen to be a civil engineer. So unless it needs to be cast in concrete, it takes me a bit longer. I was even wondering if a simple 555 timer could act as a MOSFET trigger . From what i have been reading, the may be a bit slow for buzz free operations. Some tech threads recommend up into the 18khz range to limit hum and buzz.

I saw the infinite speed potential too or I thought maybe just changing fixed resistor values to recreate the three speeds (full speed is a full 12 volts).

If you come up with a circuit, i'd love to see the schematic ...
The AVR controller is pretty cheap (3 bucks). I work at Colorado Space Grant on the RockSat-9 team, we are using AVR chips on custom PCBs so we have some AVR programmers laying around that should work. Also looks like the ATtiny 85 can also be programmed with an Arduino Uno.

Infinite speed would be cool, it would depend on how easily I could modify the stock switch with a potentiometer or something else. Otherwise just using the regular switch with 4 preset resistances would work.
05-03-2013 03:23 PM
horsedad58 Freeskier, you're headed down the same path i was going.... but you clearly understand what is needed. I, unfortunately, happen to be a civil engineer. So unless it needs to be cast in concrete, it takes me a bit longer. I was even wondering if a simple 555 timer could act as a MOSFET trigger . From what i have been reading, the may be a bit slow for buzz free operations. Some tech threads recommend up into the 18khz range to limit hum and buzz.

I saw the infinite speed potential too or I thought maybe just changing fixed resistor values to recreate the three speeds (full speed is a full 12 volts).

If you come up with a circuit, i'd love to see the schematic ...
05-03-2013 02:42 PM
freeskier I really hate how Chrysler did the blower motor in our Jeeps, mine needs to be replaced and I've already melted my resistor pack connector once. I think I'm going to experiment with this, I have the resources...

I'm looking at a MOSFET IRF540, which is rated for 27 amps, then an optocoupler that way the MOSFET gate can run off the 12v from the Jeep and not a low voltage from a controller. An ATtiny85 looks like it would be the perfect controller. It has two PWM outputs and can be boot loaded with Arduino.

All this could be put on a custom PCB that would fit into the existing resistor pack opening that way it would still be cooled. PCB would be the most expensive part, but a final design should be cheaper than a new resistor pack.
05-03-2013 02:05 PM
freeskier
Quote:
Originally Posted by horsedad58 View Post
Not sure about the exact number but i believe it's somewhere between 10 and 15 amps.

I have an 05 and the whole system did the meltdown thing. For the near term I opted to go the replacement route for all (controls, blower motor and resistor unit) and it came in a little under $200. The new blower was a non Chrysler unit so I hope it will go a ways before another overheat. The old unit lasted 6 yrs. That should me some time to figure out a better answer. I am looking at pulse width modulation for speed control. There's a lot of ideas and suggestions on the web concerning automotive use with the upside being less heat and power loss at lower speeds. The downside is it's a little above my understanding right now...
Dang, can't believe I didn't think of this. H-bridge controllers are great at controlling motors and would give you a near infinite speed control. The issue might be current, my team is currently using them to control some peltier units, but those have a max draw around 4 amps. We did initial testing using motors and they work great.

I bet I could whip up a simple circuit in Eagle and use a controller boot loaded with Arduino, the code would be pretty simple. You could even swap the in dash switch for a potentiometer and have "infinite speeds".

EDIT: Just realized we are using h bridges because current needs to be reversed. A regular transistor with an Arduino controller would work well because they have PWM functionality.
05-03-2013 12:38 PM
flynhi4u
That would be a better way

That would be a better way to control the speed but it would require extra components like a pc board with a speed controller. Not sure how you would tie that into the existing system. Our aerial camera using pule width modulation to control the motors in it.
I could fix mine like you did yours and hope for the best. Our jeep will not be our daily driver so it won't see a lot of use. Do you remember what brand motor you replaced yours with?
05-03-2013 11:21 AM
horsedad58 Not sure about the exact number but i believe it's somewhere between 10 and 15 amps.

I have an 05 and the whole system did the meltdown thing. For the near term I opted to go the replacement route for all (controls, blower motor and resistor unit) and it came in a little under $200. The new blower was a non Chrysler unit so I hope it will go a ways before another overheat. The old unit lasted 6 yrs. That should me some time to figure out a better answer. I am looking at pulse width modulation for speed control. There's a lot of ideas and suggestions on the web concerning automotive use with the upside being less heat and power loss at lower speeds. The downside is it's a little above my understanding right now...
05-03-2013 10:42 AM
flynhi4u
Blower motor thoughts

Just got our first Jeep and of course it suffers from the blower motor issues. Ours has the melted connector on the back of the switch. I was able to jump the switch and verified that the motor would run on 4 speeds. I have read countless threads on repairs. Most agree the root cause is the motor aging and pulling more amperage than the wiring will carry causing too much heat then resulting in things melting down. I hate to put factory parts back in to only have this problem down the road as we are planning on keeping our jeep for a long time.
So I was wondering why have not read about anyone swapping out the Chrysler blower motor for another brand to eliminate the root cause of the problem? I am thinking I can go to the parts yard, find a Toyota or Nissan blower motor that I can adapt to fit, fix my wiring, install a new switch and never mess with it again. I have a Tracker that is my daily driver for now with close to 200k on it and I have never had the first issue with the blower on it.
I cannot find any detailed specs on how many amps the original motor pulls. Anyone have any idea on how many amps that would be?

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