Friday, December 31, 2010


Jacket liner is now wired and tested. Heats up nicely.
Still needs something like zipper, collar, connectors etc.

It has 11.6m heater wire (6 x 193cm) with 24.8 ohms per wire, connected parallel so if I calculate correctly resistance is about 4.1 ohms.
With 14volts it gives 47 watts of power?

Tuesday, December 21, 2010

Jacket taking shape.

Jacket is progressing nicely. Or perhaps "jacket" is not a right term here, it is more like flannel shirt with 16 meters of heater wire in it.

Wednesday, December 15, 2010

Jacket progress

Not a jacket yet but kinda backwarmer.
I have tested this now couple days (in the mornings, daytime is too warm) and it is absolutely marvelous.

Two 2.1meter (210cm) loops of resistance wire connected parallel (about 27ohms each), power directly from bike. That makes two ~7watt heating elements.
Heats to 34C.

Works ok if temperature is around +3C as long as speed does not go over 80km/h.
Over 80 it does not feel warm, I need to cut 10-20cm off from wires. That makes it run a little warmer, around 40C-50C max. Should be enough and it will also prevent burning if controller fails and connects battery straight to jacket.

Thursday, December 9, 2010

But how the box itself...

Just received components for heat controllers today:
Microchip PIC 18F2331
Potentiometers (how to make them waterproof?)
Logic level mosfets

Still one open item is: how the user interface should look/work? Lots of ideas but now when it is time to actually put something together... Yeah.

How about this:

How it works? Well...
Normally two rotary knobs in front controls the heat of two "channels" (gloves+jacket, boots+pants).
Two rotary knobs on top control the balance of heat on two areas: gloves/jacket and boot/pants.

Simple, eh? Ok, let me explain more: front knobs control the heat on upper and lower body.
Top knobs are just temporary. With them the heat balance can be adjusted (gloves vs jacket and boots vs pants). Once top part is removed (magnetically attached), front knobs raise/lower heat on respective body parts.

This design may change though...

Friday, December 3, 2010

Field test done!


What a difference!
Couple times riding to work in the morning in below 40F weather wearing these prototypes...

And once riding back from work them stuffed inside the jacket.

Yep. I will definitely make jacket liner, pants and socks (or insoles) too.

About the controller... After spending several nights with microcontrollers, oscilloscope, soldering iron, datasheets and several glasses of wine I realised I could do it with 555 timer chip and some passive components...

About 10 minutes later:

PWM controlled mosfet, kinda like dimmer, capable of handling up to 18 volts / 10 amps.

Overall cost (without cables and connectors but including the plastic box: $5).

And here is the prototype box in the left fairing pocket of my 'wing:

So what's next?
Do "final" gloves, jacket liner, underpants (or perhaps chaps?) and insoles (or socks).
Oh, and the controller. Two channel controller should be sufficient.

And then, perhaps, some kind of wireless thermostat controlled four channel version of controller... Actually it is almost ready but I want to get warm now, not when the software is ready...

Monday, November 29, 2010

Second glove... no field test yet.

Did the second glove.
Resistance is 18.0 ohms so it is pretty darn close to the other glove (without measuring the wire length before sewing it...)

Also did the Y-wire for connecting both gloves to controller.
Oh, and the controller is ready... sort of. Still needs to be soldered together but on breadboard it works just fine.
The only problem is: it is a single channel. And the reason for that is laziness...

Heat controller is microcontroller-based. PIC18F2580 has a builtin PWM-module, ADC input reads the value from 10k potentiometer and sets the PWM duty cycle based on potentiometer position, logic level MOSFET, connected to PWM output, controls voltage flow to gloves.
Could not be simpler than that.

In the test setup above, PWM duty cycle (Max) is about 300uS, period is 1.3mS. That gives gloves 6.7volts and that makes the wire to heat up to 48C-degrees.
Turning the potentiometer counterclockwise turns the heat down.

Next I need a plastic box to house the electronics.

Friday, November 26, 2010

First glove prototype ready and tested!

About one hour and 1.5meters of heater wire later:

Test rig:

Test result:

Excellent! The second lowest setting gives nice and toasty+38C temperature.
(The second highest setting gives +85C... Crispy?)

That means I can lower the pwm frequency and get the highest temperature down to +40C and that way there will be more precise temperature control. (Don't worry if you don't understand. Neither do I...)

Calculated heating power is about 10 watts. Tomorrow I will do the other glove and set them to be in series, that will lower the total power to 5 watts. Should be enough and that will also keep current draw in around 0.4 amps.

If all goes well, I will perform field test on saturday. Weather forecast says it will be a cold day. Just above freezing in the morning. Perfect weather for testing.

Saturday, November 20, 2010

UI getting ready...

It's time to close the lab for today.
Today I got the user interface sorted out.
Works more or less like this:

One number display, one knob to rotate, one button (will be embedded to knob later).

There will be four "channels" for four different heating circuits: Feet, hands, legs and torso. (Perhaps Socks, Gloves, Pants and Jacket)

Each channel has its own heat setting, in default mode device adjusts all channels equal amount up or down.

In default mode (right after powerup) display shows the global heat setting (ten levels 0-9).
With knob user can change this setting.

If user pushes button for more than a second, display starts blinking and shows the channel (S,G,P or J).
User selects desired channel with knob and pushes button for less than a second.
Display keeps blinking (indicates individual channel setting in progress).
Now user can set selected channel temperature, again ten levels 0-9.

After selecting desired heat level, user pushes button for less than a second and display starts blinking the channel id again (S,G,P or J).

Now user can either select another channel or push more than a second and device goes back to default.

Should be something like that but I have a feeling it needs some more thinking...

Wednesday, November 17, 2010

Getting cold...

'bout week ago we were riding around northern Arkansas with some pals. It was not exactly freezing but it sure was freaking cold in the morning(s).

Ok, it was below freezing but not much.

One of us had electrically heated clothes so he was the only one feeling warm and cozy no matter how cold the weather got.

Now when I checked the prices of such clothing, it made me think "How hard could it be"...
I definitely will not pay $1k for socks, gloves, vest and pants. No way!

Google found me some DIYers who have made heated clothes out of 30gauge hook up wire. I formed a plan to make heated insoles for my boots with such wire.

I told about this idea to fellow tinkerer Esko and he found one company, in internet of course (, who sells heater wire (or resistance wire).
I just ordered 50ft spool of "33 Gauge 3/38 Stranded Midohm/Alloy 180 w/8 Mils Tefzel"

In plain English that is 0.18mm diameter teflon (PTFE) insulated nickel+copper wire with nominal resistance of 3.572ohm per foot. Thin enough to me sewn into jacket liner etc. with a needle.

For controlling the heat I already have, from my flight simulator project, a pcb board with Microchip PIC 18F2580. That combined with logic level mosfets and some pwm-code will do a nice heat controller.

Stay tuned...