12 volts voltage regulation with Picaxe?

[Bob Champagne]

First let me say that before discovering this site I knew absolutely nothing about microcontrolers, but after reading and reading the so many informative posts, I have now completed several simple Picaxe projects. Thanks all.
Now the question: I have a VTT with heated grips that I control the temperature with a selfmade PWM circuit, instead of the usual LOW-HIGH switch. But the voltage from the alternator varies with the RPM of the motor between 12.4 and 14.2 volts, and so does the temperature of the grips. Is there a way to get a stabilized 12 volts using a Picaxe?
Thanks in advance, Bob.

 

[redpawn]

Another Approach?

I would not try to regulate the voltage to 12V as you voltage is not much above 12V in the first place. You should be able to adjust the PWM duty cycle based on the voltage produced by your alternator. Assuming you are using a voltage regulator on your picaxe you could use a voltage divider to read a scaled down version of the voltage from your alternator using the ADC command. If you use 10K and 30K ohms of resistance in the divider you will be able to read the 1/4 of the alternator voltage. Use a protection resistor on the input pin and make sure that your system shares a common ground for voltage reference. Take great care when working with vehicles as you can really mess things up if things go wrong.

 

[BCJKiwi]

Is it possible to sense the temperature of the grip?
If so, adjust PWM using the desired temperature as the reference.

 

[inglewoodpete]

Since you actually want a regulated temperature, it might be better to use the grip temperature as the feedback mechanism. The DS18B20 sensor and ReadTemp can be used to provide input to the PWM routine.

At the moment we need grip coolers in Oz! Any ideas?

 

[papaof2]

grip cooler

At the moment we need grip coolers in Oz! Any ideas?

Peltier effect modules, powered by the vehicle's 12 volt system and controlled by a PICAXE + DS18B20 with a fan pushing the cooled air through some small diameter tubing and directly onto your hands. For greater effect, wear one-size-too-large rubber gloves with a small hole in each fingertip of the glove and feed the cooled air into the wrist of the gloves to have it circulate around the hand and each finger.

You did NOT ask for *practical* ideas ;-)

John

 

[andrewpro]

Peltier effect modules, powered by the vehicle's 12 volt system and controlled by a PICAXE + DS18B20 with a fan pushing the cooled air through some small diameter tubing and directly onto your hands. For greater effect, wear one-size-too-large rubber gloves with a small hole in each fingertip of the glove and feed the cooled air into the wrist of the gloves to have it circulate around the hand and each finger.

You did NOT ask for *practical* ideas ;-)

John

Bah! Air is a poor heat transfer mechanism! I agree with the peltier junctions, but I think you should use a closed loop ammonia system winding through a heat sink in some tubing attached to the PJ. Then with a high powered H-Bridge controlled by the picaxe and PWM, you should be able to make it hot or cold or anywhere in between from instant frostbite to 2nd degree burns

--andy P

 

[D n T]

Cooled grips

With regard to voltage monitoring...
I want to monitor a max of 24 volts using an ADC input to a PICAXE my thoughts are:
24 volts-------------
|
40K resistor
|
|---- to PICAXE
|
10K resistor
|
0 volts------------------

I think that will give me a max PICAXE input of 4.8 volts? Am I correct in my assumptions, because I want to keep the magic smoke inside the chip.

Using Peltier cells...
I built a stubby holder that uses 8 Peltier cells and nearly freezes my coke cans, it made out of a block of aluminium that I turned the centre out of and mounted two cells vertically on the four sides, then mounted milled aluminium heatsinks to them. It could mount in a ski boat and keep my can cold until I finish my run, mind you if I leave it ashore I'm sure I would get about another 3 - 4 knots out of the boat ( less weight), but wheres the fun in that.

Stemming from that, mount the peltiers inside the gloves onto a piece of aluminium shaped to rest on the back of you hand and a temp sensor under it.
You would need to mount a heat sink on the hot side on the outside of the glove, so cutting the glove is required to make contact between the peltier and the heat sink, but the air flow over the heat sinks would garantee the peltiers would stay cooool.

Just make sure the top of the heatsink won't impale you if your bike decides you should get off at over about 20 Km/h

ALTERNATE SOLUTION: BUY A CAR WITH AIR CONDITIONING AND DOORS , much safer?