Sunday, December 22, 2013

PWM Grip and Jacket Heater Controller

A variable output controller for grip heaters or heated clothing costs around $75. We decided to build our own.

We found this schematic at This is a "Pulse Width Modulation (PWM)" power controller. It is basically an oscillator which switches the power transistor on and off with the relation between on time and off time ("duty cycle") set by the potentiometer position.

In the schematic, the "DC Motor" represents the power load, which actually will be the heating element. Another modification is the potentiometer has a SPST switch which is used to control power to the circuit. In the case of the grip heaters, where the load is permanently connected, a relay is used to connect power to the load (called "+V MOTOR" in the diagram above.) This is done to prevent any possible drain on the battery when the grip heaters are not being used. Finally, the C1 capacitor was changed from 0.1 to 10.0 uF in order to slow the pulse rate down (from about 144 Hz to 1.4 Hz) so as to prevent possible disturbance to the motorcycle electronics.

(To be continued.) The grip heater controller was built and is in operation. Unfortunately, we forgot to take any photos. Hopefully, there will be construction photos of the jacket controller...

Heated Jacket Liner

This is a DIY heated jacket liner for use under our motorcycle jacket.

It was constructed by stitching a 20 foot length of heater wire from a defunct electric blanket to the inside of the red windbreaker. The green windbreaker was sewn inside the red one to protect the wires.
The white wire is the heating element. The black one is an 18AWG wire running from one end of the heating wire to the external connector at the bottom of the jacket.
Here is the routing of the wires.

The electric blanket wire is a twin conductor wire. Each conductor is made of a pair of 36 AWG strands spiral wound around what appears to be a nylon fiber core, and coated with a plastic insulation of some sort.

The external connector is a 5.5 x 2.1 mm DC power connector - similar to those used for laptop computer power supplies.

Each conductor of the heating wire has a room temperature resistance of approximately .24 ohms/foot. In the jacket, the two conductors are wired in parallel, giving a total resistance (with connections) of approximately 2.5 ohms. At 12 volts, the current starts at 4.8 amps, resulting in an initial power of 58 watts.
As the jacket heats up, the resistance increases slightly, dropping the power to around 47 watts. That is pretty low for a jacket; 70-90 watts is more typical. But as this was the first try, 47 is acceptable. It produces a noticeable amount of warmth.

Friday, November 15, 2013

V-Strom Windshield Mounting Bracket - Madstad At Last

We finally gave up trying to fix the windshield turbulence problem using a home-made mounting, and purchased a V-Strom Windshield Mounting Bracket from Madstad Engineering. It provides a range of height and slant adjustment for the windshield.

The new windshield profile shows it it a couple of inches forward and upward from the home-made brackets. This has pretty much solved the helmet buffeting problem.

The best position is rider-dependent. For me, it is raised up 3/4 of the vertical range and tilted back 2/3 of the tilt range. In my normal riding position, my eyes are 21 inches up and 12 inches back from the gas tank filler cap.

Sometimes DIY isn't better...

Tuesday, October 29, 2013

V-Strom Accessory Bracket

We needed a place to put a 12 volt power outlet (aka cigarette lighter socket) and a switch for grip heaters.

Using this template

...we cut and formed a piece of .093 aluminum sheet salvaged from a trailer fender.
The back side looks like this:
And here it is installed.
The control for the grip heaters will be added when it is finished.

Tuesday, July 30, 2013

"HappyStad" Vstrom Windshield Modification

The Suzuki V-Strom windshield in its stock configuration causes severe helmet buffeting, due primarily to its rather upright angle.

Here is a simple modification that rotates the slope of the windshield back about 19 degrees.

We cut a set of spacers from 1/2" schedule 40 PVC pipe, using the miter guide on a table saw.

This view shows the angle a little better. The longer spacers are 26mm at the high side, and 20 at the low side. The angle of the cut is 19 degrees.

The spacers are installed between the fairing and the stock windshield bracket. We used 6x30mm pan head bolts on top, and 6x40mm on the bottom.

Here's a view from the front.

At this angle, the windshield aligns pretty well with the slope of the fairing.

Buffeting is reduced, but not eliminated. For a person with eyes positioned 20.5 inches above the tank filler cap, the air flow from the top of the windshield hits about forehead level.

Next step is extending the height of the windshield.

After further experimentation using cardboard windscreens of various sizes and configurations, I gave up and purchased a Madstad Adjustable Windshield Mount.
With the OEM windshield positioned about 3/4 of max height and 2/3 rearward tilt, the vision-blurring buffeting is mostly gone, up to 75mph.
Good enough for me.