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Discussion Starter · #1 ·
So I ordered one of those $280.00 C6 ZO6 steering wheel off of e-bay, the "D" or flat bottom steering wheel. I got the steering wheel in and I will be removing the perforated vinyl from the steering wheel. On the wheel I got only the right and left side of the wheel is vinyl and the top and bottom are carbon fiber. I am only going to be able to heat the areas that are vinyl wrapped.

The steering wheel grip is not round anywhere on it so that is going to make it a bit of a challenge to get 100% coverage of heat. I am not going to use a heating element in the traditional sense to create the heat. I had found a company called carbon heater that has a fabric type of heating element. I e-mailed this company and got no response and upon further investigation I found out it is in fact not a company but a single person and that person lives in the Ukraine.. So I am not gong to be ordering from him because it is sketchy and the lack of a response to my email pretty much solidified me not buying from him.

I did do some research into what the fabric is that he is using and found that it is carbon fiber. I did research into whether carbon fiber does conduct electricity and that it does have a resistance to it and all of that checks out. The type of carbon fiver he is using is called 1K which is a super fine flexible version of carbon fiber and it is suited for use in clothing because of it's flexibility. I am not going to be putting this in clothing so I do not need to have that kind of a flexibility. So I ordered 2 yards of 3" wide 3K carbon fiber tape from a composites supplier. The cost of the carbon fiber tape is 30.00 shipped. So not too bad.


Once I get the vinyl off I will be using 3M super 90 spray adhesive to bond the carbon fiber to the steering wheel and then I will be wrapping the wheel with a layer of Kapton (polymide) which is a non conductive adhesive backed and heat stable to 450°F or so. It is non conductive and it is a plastic so it will keep liquids from getting to the carbon fiber.

The nice thing about using the carbon fiber as the heating elements is it is going to warm up evenly and not in areas where there is an element or a wire.

To adjust the temperature of the element all I have to do is change the voltage being supplied to the carbon fiber. This is easily done using a variable LDO (Low Drop Out) voltage regulator. The one I am going to be using for this project is the LM1084 which is accurate to +- 0.1% on the output voltage and has a maximum current rating of 5 amps. I am able to adjust the output voltage of the regulator and I will be using an NPN transistor to turn the voltage regulator on and off. I will be using PWM to rapidly turn on and off the power supply to the heaters to control the temperature beyond what I am able to do with adjusting the voltage alone.

I will be using film NTC thermistors as temperature probes and they have a range of -40°F to 392°F, more then enough range. The thermistors are 0.2mm thick so they will not be able to be felt in the wheel. I am going to collect temperature reading from 10 location on the steering wheel. This is so I know what the temperature is under a persons hand to be able to make adjustments needed to keep the heater in the proper temperature zone. This single aspect if the largest failure of the design of an OE heated steering wheel. I am sure anyone that has operated a vehicle with one installed noticed that if they do not move their hand pretty often it will get hotter and hotter where they are gripping the wheel. This is because your hand insulates the heater so the heat doesn't dissipate as quickly in the areas that you do not have your hand. An OE heated steering wheel has a single temperature sensor and that sensor is only there to make sure the heater doesn't over heat. OE steering wheels regulate the temperature based on how long they are on and off for and not by what the actual temperature of the wheel is. If the temperature is rising above the set point the PWM controlling the duty cycle of the heater will be adjusted which will raise and lower the power going to the heater and in turn will raise or lower the temperature of the heater.

There is some complex math that I am going to have to use as well as put into place a learning routine that will map out how fast the temperature rise and fall is so the program will be able to know that if it needs to make an adjustment of say 10 degrees it will know what it needs to set the PWM signal to. The learning is something that will be constantly running while the heaters are on because of ambient temperature changes which will effect what the wheel temperature is.

I did ordered most of the parts needed and I am going to start writing the code to control everything. My plan is to hyjack the steering wheel controls when a button combination is pressed and that will decouple the radio steering wheel controls from the vehicle so they can be sued to adjust the temperature of the heaters.
 

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if it were me doing this I would end up with a afu 300$ paper weight, and not a pretty one either....my days of doing this kind of stuff are gone.hell nowdays I cant even seem to get the $$ sign in the right place:oops:.. thankfuly hear in florida I dont think Ill ever need a wheel heater. just a dollar store wheel sock works fine. I'll have the wife re wrap the wheel in leather at some point.( should of done that when I had it off for 2 months)
Good luck with the project!!!
 

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Discussion Starter · #4 ·
The only thing is if I will be able to use the perforated vinyl again. It all depends o the quality of the adhesive they used. If I can't I am going to have to break out the sewing machine to put a stitch down each edge where it gets sewn together on a new piece of leather or vinyl.

I am going to have to cut the carbon fiber I bought because I was a ding ding and should have gotten the 1" instead of the 3". The 3" has too low a resistance and I would have to power it using a really low voltage in order to keep the current draw in check. I am going to make 1/2" wide strips and 7 of them will need to be used on each side of the steering wheel to make it around the whole hand grip.But now that I think about it instead of going in a straight line I can wrap it around and make it longer and use a wider strip which would be better then having to series/parallel the strips together to get the correct resistance.
 

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I admire your design complexity!

Never had a heated wheel, so this is just a question, but isn't it just a case of wanting the wheel to heat when you first get into the cold car? Then you can turn it off when the car has warmed up?

As a side note, many of us have installed seat heaters (me in a couple of cars) and the heating elements in those are carbon fiber too - I assume for flexibility. Only long strands in a flattened bundle about 1/4" wide for each element, rather than woven, but same principle.

Cool!! (or... hot!!?)
 

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2008 Pontiac Solstice GXP - Mysterious
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KG, a question...
Is there any concern of the adhesive on the Kapton layer getting "gooey" from being on top of the heated CF?
 

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Discussion Starter · #7 ·
thanks @TomatoSoup for the kind words.

I am one of those people that doesn't really like hot air being blown on me and I have found that between the seat heaters and a heated steering wheel I do not need to use the heat in the vehicle at all. I find it much more comfortable to drive. I also have pretty bad arthritis and holding onto a cold steering wheel doesn't feel all that great and wearing thick insulated gloves while drive is not a fantastic idea.


I did start working on the wheel and took the vinyl off one side of it. I have to say it came off pretty easily so that's not a great thing in the durability department. The glue was on the sparse side.. I did however correct the annoyances in the grip areas.

Here are some photos,

Eye Leg Automotive tire Jaw Finger



This here was the largest annoyance. The steering wheel getting thicker on the back side.

Tire Ruler Wheel Automotive tire Bicycle tire


Finger Gesture Font Fish Thumb



and now corrected
Automotive tire Wood Automotive exterior Bumper Fender


Ruler Wood Office ruler Finger Measuring instrument


Huge difference there.

Second largest annoyance.

Hood Automotive tire Wood Fender Synthetic rubber
Tire Wheel Automotive tire Tread Bicycle tire



and now corrected

Automotive tire Wood Tread Rim Bumper


so now the steering wheel is going to only get thicker on the front right where the hand grip is, It is going to be a consistent shape except for the flat bottom around the outside.

While it is stated that the steering wheel is carbon fiber on the top and the bottom it is not. It looks to be a carbon fiber sticker and then it had clear plastic put over the top of it, probably injection molded.

With the corrections and also some changes to the grips so you can get a thumb around the wheel if wanted makes it feel a whole lot better.
 

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Discussion Starter · #8 ·
@HHGadget, no there isn't the glue is heat stable to some 450°F. Kapton is used as a heat transfer medium for doing things like iron on vinyl prints onto clothing and that type of thing.
 
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Discussion Starter · #9 ·
OK first build pic.

I have the wiring installed on one side of the steering wheel for the heating element and I also have te 5 temperature sensors for the one side installed with associated wring.


Sleeve Bag Denim Electric blue Rock-climbing equipment


I used a dremil tool with an end mill to cut grooves the wires rest into. I the shot the edges and insides of the grooves with super 90+ adhesive and put the wires into place. I had already soldered the wires to the temperature sensors. then places the Kapton tape over the wire and he sensors. Had to be careful not to go to deep when making the groove so a bump wouldn't be felt in the steering wheel.

I placed the temperature sensors in locations that a hand would normally be at. Next step is applying the carbon fiber and then stitching the wires into the fiber at the ends
 

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In Colorado it gets COLD in the winter. My commute is 20 minutes each way and it can be -20 when I get the truck going. The heated seats and wheel are not a nice to have. My routine is I turn the wheel and seats on at start up and turn the seats off about half way to work as my butt is toasty. The wheel stay on for the commute and is very enjoyable. For longer drives, I do tend to turn the wheel off after about half an hour.
 

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Discussion Starter · #11 ·
I turn them both on when starting out and about 15 minutes or so into my drive I turn the seat to it's lowest setting. I only have one setting for the steering wheel. I will initially run the heater in the car to get rid of the chill then I shut it off once the heated steering wheel and seat get warmed up. Right about the time that I lower the heat from the seat is about when I open the window 2 inches or so. I like the fresh air, The only time I use air conditioning a car is to initially cool the inside down some or f there is someone else in the car with me that wants the AC on. Same deal with the heat n the car as well.

I do use the air conditioning to thaw out a frozen windshield.
 

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Discussion Starter · #12 ·
The Carbon fiber is really funky.

A piece that is 47" long and 1" wide has a resistance of approximately 16 ohms. a piece that is 10" long and 1" wide has a resistance of 2 ohms. Now sure how that math works out but it is apparent that the ohm increase is not linear. Then if you take a piece that is 3" wide and 10" long you get 8 ohms. hmmmm... OK so triple the width would be 3 resistors running in parallel which should be 0.67ohms not 8 ohms. There is no standard resistor calculation that can be used to come out with 8 ohms...

I don't think I bought enough carbon fiber to do all of the testing needed Because I need to be at 6.25 to 7.0 ohms per side if I connect them in parallel or 1.55 to 1.75 ohms per side if I connect them in series. My target is a total of 3.1 to 3.5 ohms of resistance. This will keep the current draw below 4.5 amps at 15 volts.

I just thought of something. Because I am going to be using an adjustable power supply to feed the heaters If I measure the input voltage I can adjust the power supply so it will never go above 13.8 volts.

Gonna have to do some thinking about the math on that one because I am going to need to get a voltage divider into the mix. I should be able to size the voltage divider so at 15 volts input the output from the divider would be 3.3 volts. so a simple remap


old_min = 0.0
old_max = 3.3

new_min = 0.0
new_max = 15.0

voltage = 3.04

new_voltage = (((voltage - old_min) * (new_max - new_min)) / (old_max - old_min)) + new_min

new_voltage = 13.82

So the controller only can take a 0 to 3.3 volt input on it's pins otherwise it will cook. so I have to lower the voltage coming in. by using 2 resistors this can be done and that is called a voltage divider. and the math to figure out the voltage output from the divider is

resistor1 = 350.0
resistor = 100.0
volts_in = 15.0

volts_out = volts_in * resistor2 / (resistor1 + resistor2)

volts_out = 3.33

essentially the voltage divider is a factor.
factor = resistor2 / (resistor1 + resistor2)
factor = 0.2222222222222222

so when I read the voltage on the pin I can then turn it back into the voltage that is before the divider by doing the following

3.33 / 0.2222222222222222 = 14.99

I need the voltage before the divider because that number needs to be used in the calculation to know how to adjust the power supply for the heaters. Because the power supply is adjusted by using it's input voltage as a reference and I set a percentage of that. So if the input into the power supply is 13.8 volts and I want to output 13.8 volts I tell the power supply 100% but if the input voltage is 15 volts and I want 13.8 on the output I cannot tell the power supply to set it to 100% like I did before because that would be too much output. I need to tell it to output 92%.

Because the voltage see in a car is not a constant and it can vary anywhere from 9 volts up to 15 volts and I need to have a constant as a starting point for the heaters and that constant need to be the maximum amount of current and the current is calculated by how much voltage the heaters see and the resistance of the heaters The constant I need would be the absolute maximum voltage I can allow the heaters to see at any point in time. The higher the voltage the hotter the heaters are going to get and the higher the current draw will be.

I still have to figure out how hot the heaters will get based on the amount of voltage I feed in. I am sure this is also not going to be linear and I will need to figure out what the factor is for a voltage to temperature mapping. Right now I am using 13.8 volts because that is the typical voltage of a running car. It may be higher or it may be lower. the maximum voltage the heaters will see is going to be whichever is the lower number; either 13.8 or the voltage in the car. If 13.8 volts makes the heater to hot then I will use a lower number.
 

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It is interesting, I have never used a heated wheel. It gets very cold here as well. I do not even like heated seats. Perhaps if I had a heated seat/wheel combo I would change my mind. Never had it so I don't miss it syndrome.
This is an aspirational mod and you are doing a good job of it.

For the calcs, you list your factor as 0.2222222222222222. There is only 1 significant digit in your input number so there can only be one signifigant digit in the result. So for this calc 0.2 is correct and the rest of the '2s' are just noise. A helpful hint to save time. It was a question on my PE exam so I always remembered it.

I will follow this not because I intend to do it but just to watch your creativity.
 

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Discussion Starter · #14 ·
OK I gotta say I lucked out like you wouldn't believe.

So I decided to take the 3" wide 3' line piece I have and simply wrap one side. I took a piece of 26 gauge stranded wire and stripped off about 12" of the insulation. I then lightly tinne the wire with solder. has to be done lightly so the wire keeps it's flexibility but no stray strands would be sticking out.

The way the steering wheel is made there is a gap between where the vinyl wrap ends and the carbon fiber portion of the steering wheel starts. That gap is where the vinyl gets tucked into to make it look nice So what I did was I wrapped past each of the gaps. I then took the tinned pieces of wire (2 of them) and one on each end I pushed them into the gap ll the way around the wheel. I left enough wire long enough to twist the ends together. When I did this the wire pulled deeper into the gap pulling the carbon fiber heating element with it. Doing this does several things, it makes the wire have a nice static contact with the carbon fiber heating element. It's a way to terminate the element in a manner where it will not become loose. It is also a nice way to evenly spread the voltage and current around the entire element. Because the heater element is wrapped around the wheel there is 100% coverage. I do have each wind slightly overlapping. When I test the resistance I get 1.6 ohms which landed exactly where it needs to be to be able to join the 2 elements together and get into that 3.1 to 3.5 ohm window.

I am tickled to death it worked. I am also going to end up with 100% coverage!!!!

There are 2 open spaces in the clock spring. one for power and one for ground. The controller for the heaters is going to be powered by an ignition wire that is already ran into the steering wheel. and the ground for the controller is again already ran into the steering wheel.

3.2 ohms of of resistance at 13.8 volts has a current draw of 4.3125 amps which is a nice place to be because the maximum current that can go through the clock spring is 5 amps.

That being said4.3 amps is a HUGE amount of power and I suspect that the heater will get crazy hot as in boil water kind of hot. so if I use the minimum voltage of 1 and a maximum voltage of 8 the current draw will be 0.3125amps to 2.5 amps which seems to be a better number to get the wheel warm and no hot enough to burn. That is the reason why I am putting the temperature sensors in, to keep it from getting too hot.
 

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Discussion Starter · #15 ·
For the calcs, you list your factor as 0.2222222222222222. There is only 1 significant digit in your input number so there can only be one signifigant digit in the result. So for this calc 0.2 is correct and the rest of the '2s' are just noise. A helpful hint to save time. It was a question on my PE exam so I always remembered it.
I just did some fast floating point math and I didn't make any corrections for errors.

BUT.. If I do what you say and 3.3 / 0.2 the result is wayyyyyy off.

3.3 / 0.2 = 16.499999999999996

When I compensated for floating point math error these are the real and exact numbers

volts * resistance2 / (resistance1 + resistance2)
15 * 100 / (100 + 350) = 3.333333333333333333333333333

resistance2 / (resistance1 + resistance2)
100 / (100 + 350) = 0.2222222222222222222222222222

3.333333333333333333333333333 / 0.2222222222222222222222222222 = 15
 

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It's more of an engineering precision thing. For instance, if you can measure a voltage to the milivolt (.001), A resulting calculation can only be correct to those three significant figures. So if you calculate say a current from it via ohms law the current would only be correct to 3 significant digits. So you would end up with something like .123 ohms, it should never be .1234567, the 4567 portion is extraneous and you can never prove it is correct due to your ability to measure the numbers that went into the calc out to that number of decimal points.
Why am I bringing it up? Not sure, was just an interesting thought in my head when I saw all the 2's. Took me back to my exam.
Sorry, don't mean to derail your thread
 

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Discussion Starter · #17 ·
No it's cool. It's just that using that methodology causes gross computational errors.

Because what you are saying is the calculations should be like this.

volts * resistance2 / (resistance1 + resistance2)
15 * 100 / (100 + 350) = 3.333333333333333333333333333
because there is no decimal precision the result would be 3

resistance2 / (resistance1 + resistance2)
100 / (100 + 350) = 0.2222222222222222222222222222
again because there is no decimal precision the value here would be 0

3.333333333333333333333333333 / 0.2222222222222222222222222222 = 15
This would be wrong then and the correct equation would be

3 / 0

which is a zero division mathematical error..

Not sure as to why your engineering test stated that the result of an equation should have the same decimal precision as which ever input value has the highest decimal precision. That has a high probably of producing erroneous results. It is not the first time I have come across that either the SI standard is also the same way. I recently wrote a program for doing unit conversions that's why I know about the SI standard doing the same thing that you said with the decimal precision of the results.

I just find it baffling why someone should have to write equations like this

15.000000000000000000000000000 * 100.000000000000000000000000000 / (100.000000000000000000000000000 + 350.000000000000000000000000000) = 3.333333333333333333333333333

100.0000000000000000000000000000 / (100.0000000000000000000000000000 + 350.0000000000000000000000000000) = 0.2222222222222222222222222222

in order to do the reverse math and end up back at the correct input values.
 

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A piece that is 47" long and 1" wide has a resistance of approximately 16 ohms. a piece that is 10" long and 1" wide has a resistance of 2 ohms. Now sure how that math works out but it is apparent that the ohm increase is not linear. Then if you take a piece that is 3" wide and 10" long you get 8 ohms. hmmmm... OK so triple the width would be 3 resistors running in parallel which should be 0.67ohms not 8 ohms. There is no standard resistor calculation that can be used to come out with 8 ohms...
I wonder if this is just sample variablilty? If I recall correctly, you bought standard woven carbon fiber, not stuff design for a heating element. If so, you probably have multiple strands linearly with variability in length and contact points, all of which could lead to variable resistances per piece.
 

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Discussion Starter · #19 ·
The only difference between "standard" woven stuff and the stuff that is sold no carbonheating is the tow. The tow used in carbonheaters tape is 1K and the stuff I am using is 3K. 1K is a softer material. 6K is the "norm" that is used and 12K and above is used for structural purposes.

I also made a mistake when I said that a piece of 3" wide that is 10" long is 8 ohms of resistance. It is actually 2 ohms.

I have one side done to the point where I can wrap it with the vinyl. The carbon fiber is glued on and I have it all wrapped in Kapton. I stripped the insulation off of some solid 28 gauge wire I had and I pushed the insulation down into the bottom of the gaps at either end of the hand grip. I did this because the core of a steering wheel is usually metal and because I cannot really see down into the gaps to determine if it is metal I decided o caution on the safe side. I wanted to make sure the carbon heater and the wire I am using to hold it in place and also supply the power is not going to touch the metal core. Once I did that I used 3M super 90 spray adhesive and sprayed the grip and one side of the carbon fiber tape. Once the glue dried I wrapped the carbon fiber around the grip making sure to pull it tight and making sure it is also without any wrinkles. I then took the wire that I tinned and using the back of a razor knife I pushed the wire and the carbon fiver down into the gaps all the way around the grip on the steering wheel. I then twisted the wire together which tightened it and pulled it down into the gap further. Little bit of soldered to solder that wire to the power and ground wires that feed the grip and pushed the soldered piece down into the gap. I then made a piece of string out of Kapton tape and would that around the grip pushing it down into the gap on top of the wire. Then I wrapped the entire grip in Kapton. The reason for the Kapton is to keep moisture off the element That stuff is pretty strong and when I wrapped the grip I pulled it crazy tight.

I still have to check and see if the final resistance came out where I need it. I did mess up when I sprayed the glue. 3m super 90+ is like a rubber cement. It is non conductive and I didn't even think about the overlap of the carbon fiber when wrapping it. I may have to tear it all off. When I realized what I had done I already had the carbon fiber wrapped so I said screw it and decided to get to the point of vinyl wrapping it. It's extra practice so not a complete loss. I will also get to see if my idea on how to make the connections to the carbon fiber is going to work.

I had wanted to get 5" wide tape and not wrap it like I did and I may consider doing that if I did mess this up. I will have to order more carbon fiber and I will order 6' of 5" wide. The stuff I got was perfect to work with in terms if flexibility and being able to get it to contour properly. The only thing I I don't like with how it is wrapped is the overlap. While it's not going to be able to be seen in the vinyl It might be able to be felt. It's really not that bad and the vinyl might be able to get rid of feeling it. I won't know until I vinyl wrap it. There are different grades of vinyl and they will have different thickness and materials used in the backing So I may have to make a trip down out of the mountains to go to the city and see hat a fabric store has or possibly hit a car upholstery shop.
 
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Hello,

"3.2 ohms of of resistance at 13.8 volts has a current draw of 4.3125 amps which is a nice place to be because the maximum current that can go through the clock spring is 5 amps."

That's about 59 watts of heating power. I'm not sure if that's high or low. A 60 watt incandescent light bulb gets pretty warm but I've never tried to heat a steering wheel with one :)

If you're monitoring the incoming voltage to the LDO with that voltage divider, you may want higher resistor values. That 350 ohm resistor will have (15-3.3)=11.7 volts across it, and at 350 ohms, is dissipating .39 watts, so you would need a 1/2 watt resistor. A 3.3k and 1k resistor would work and you could use 1/4 watt parts.

Depending on how fast it heats, and how much thermal mass there is, you may not need anything sophisticated for the control loop. Below some minimum threshold, full power. Between the minimum and the target temperature, some linear percentage of PWM (or table lookup), and turn off the power at or above the set point. Given you're just trying to be comfortable, I would experiment with something simple like that before implementing a PID controller, etc.
 
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