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 http://www.dprg.org/tutorials/2005-11a/index.html. 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.

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...

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.

"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.

EPILOG:
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.

Making the Turnigy 9X Transmitter RF Module Removable

The Turnigy TGY-9X is an inexpensive but very functional radio control transmitter available from HobbyKing.com in Hong Kong. It is designed for replaceable RF modules, but for some reason it was built with the included module 'hard wired' in place, by virtue of the antenna wire having been soldered to the module and run thru some holes drilled in the case to the antenna position on top of the unit.

There are reasons to remove the RF module (e.g., use a different brand, use the controls with a PC simulation program), but you can't. Unless you make a mod like this. Note that the antenna has moved from the top of the unit to the back of the snap-out RF module.

Here's how I did it.

1. Remove the RF module and open it (two phillips head screws, tilt the cover out and lift upward).

2. Unsolder the antenna coax from the circuit board. Note where the shield and center conductor are attached.

3. Open the transmitter unit (six phillips head screws in back).

4. Remove the screw that holds the antenna to the case. It's inside the case, just below where the antenna enters.

5. Remove the antenna and feed the coax out through the holes. You may need to remove the circuit board attached to the back (4 phillips screws).

6. Close the transmitter up - you're done with it.d

7. Remove the screw that holds the plastic bushing to the plastic stub of the antenna. Pull the bushing off.

8. Cut 9/16 inch(15 mm) off the end of the plastic stub of the antenna mount. This is so it will fit inside the RF case.

9. CAREFULLY thread the end of the plastic stub so you can fasten it with a hex nut. I used a 1/4-20 nut on which I notched the threads with a small round file to make a 'shade-tree' die. A regular die will work, but you have to be very gentle and work it back and forth slowly so as not to twist the plastic stub off. If you break the stub off, you will have to find another way to attach it!

10. Drill a 1/4 inch (6mm) hold through the back (outside) plate of the RF box. Choose a position so the nut will clear the inside of the box. There is already a hole covered by the label which you can use to run the antenna wire through, if you position the stub hole close to it. You may need to run a drill thru the hole to clean it out and punch thru the label. I also trimmed the plastic covering of the label to clear the bushing, so I could get a good glue surface.

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11. Put the bushing back onto the antenna stub, feed the coax through the small hole, and bolt the stub up to the plate. Use superglue to secure the bushing, nut and stub.

12. Solder the coax back onto the RF circuit board. You could shorten the coax, but I didn't. Double check to make sure the shield and center conductor are not shorted together. Watch for little wire whiskers from the shield - they are tiny.

13. Reassemble the RF module into the box. I just curled the coax around in the open spaces. I also added a small lump of rubber foam to keep the circuit board from rattling.

14. Put the cover back on, and plug the RF module into the transmitter.

15. Be sure to range check the transmitter before you try to fly with it!

HK-500GT R/C Helicopter

This week, the parts for my newest helicopter kit came in from Hong Kong.

This is the HobbyKing.com HK-500GT kit.

Note that the body, rotor head and tail rotor units are factory-assembled. This makes the assembly of the kit go much quicker.

Here are the electronic parts needed to make the helicopter flyable. Clockwise from top-left:

ESC - electronic speed control (aka motor control)

Gyro - controls the tail rotor

Receiver

BEC - voltage converter for receiver and servos

Servos - actuate the controls of the heli

Battery - actually, two of them in series are used

Not shown:

Motor

Transmitter

Here is the assembled model.

Other side - more photogenic, don't you think? (It looks like there are two rotors - the black one is the shadow from the flash on top of the camera.)

The kit went together very nicely. It took me 6 or 8 hours, as I was taking my time, measuring stuff, and being careful.

This version is a mixture of CNC (metal) and FRP (fiber reinforced polymer) components. HobbyKing has cheaper and more expensive versions.