well after having a go at soldering ICs and the like i would like to have a go at making a couple of little things.

the first is a little temperature system. basically what i want is for a tri colour LED to change its colour according to the motors temperature. i was thinking about using an NTC thermistor (IIRC thats what its called) on the motor and that would power the leds someway.

and a similar thing with the tri colour LEDs but with the battery voltage. i would like to use that as the main power LED so it also gives an indication of the general voltage.

anybody good with circuits have an idea how id go about making such things?
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what you need is a comparitor do do the detection of the various states and some form of high current driver to power the LED's you will also need a regulated voltage supply to power everything (7805 will do that up to 30V input). You may be better served running it of the 5V output of the IBC but try to keep the current draw down.

darlington array might do the job or if you can find a suitablle circuit some transistors on the comparitor outputs would do, on average you want around 20 ma to drive an led, i believe the 3 colour ones will need 20 ma per active leg, (ie maximum of 40 ma)

i was thinking of making and selling such a device if you were interested

a single picaxe08 www.picaxe.com.au microprocessor will do that nicely with no other components needed except the 8 pin chip (if you power it from the IBC's 5v output).

It has analog-digital converter built in so it can measure Thermistors, you write a little bit of Basic code, which means you can set your trigger points wherever you like, and it will drive 4 LEDs directly.

You need to make a simple 3-wire cable from your PC's serial port to program it, but its worth it, they're amazingly useful little chips. Highly reccomended for anyone wanting to play with gadgetry like that.

Pickup the relevant back issues of Silicon Chip magazine (starting feb 2003 I think) for a step-by-step guide on how to get started with them.

If jake wants to start a custom-electronics store doing that sort of thing, there might be a slowly growing demmand for that. I knew of a company that made quite a good business selling all sorts of little timer, relay and so on gadgets.
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Dick Smith has several kits that may be applicable.

The first kit (K3118) uses a Dual color LED, with the above mentioned comparator, it uses a trim pot to set the transistion point for Green to Red.

If you are using SLA (K4205) has three LEDs Red/Yellow/Green and uses zeners/transistors to switch between LEDs, designed for lead acid battery thresholds.

I use the Jaycar expanded scale bargraph kit (KA1683), which has 10 LEDs showing battery status over a short range.

Of course the cheapest is to get 5 LEDs and 6 resistors (for 12V more if higher) to form a passive bargraph, of course the transistions are softer than the bargraph kit.

There are enough voltmeters indicators on the market, but a 'fuel gauge' system that would be cool, something that measures the current In or Out of the battery and integrates this to give an indication of charge remaining in the battery, I remember Philips had a chip that they used for their shavers which did this, maybe its something worthy of development.
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