Trike Lights

Step 5 Build Power Electronics

Assemble the power electronics as shown in the schematic diagram. You'll need to get everything to fit onto a 2" by 2" board or it won't fit in the project box (even then it's a little tight). Pictured is the almost-completed circuit. It lacks the white LED resistors. The heatsink for the voltage regulator is probably optional, but I had some sitting around and thought I'd play it safe.

Comments

[wobbler]

In Step 5, what is the purpose of the bridge rectifier? If you are bothered about damaging the circuit by accidentally putting a battery in wrongly, I would simply put in a single rectifier. If you're not bothered about putting the battery in the wrong way because you can't (I have a similar system on my bike but I leave the battery permanently connected and charge from a wall charger via a resistor and polarised DC connector. I have a blocking diode on that to stop both reverse current and the charger being accidentally the wrong way round. The disadvantage of putting the bridge rectifier in the primary light circuit is that it is giving two diode drops across it and will be wasting approximately 2v of the battery voltage. Putting in a single diode will at least limit the drop to 1v and also save you some money. However, if you are driving it off a dynamo it is obviously necessary, although then I would also put in a capacitor after it to smooth out any flicker.

[spyfoxy]

The plan is to have a dynamo as a power option, even though it is not currently in use. Ideally, I'd like the ability to switch between batteries and dynamo. Caps would be nice for a dynamo powered system, but the flicker isn't really that bad, barely noticable.

[wobbler]

Thanks for replying. On my bike, I use 2D cells on my current system. You can get them at up to about 10Ah which means they last a long time. The light I use for seeing by is a modified 3W torch which used 2D cells via a DC-DC chip. It is 3W Cree LED based and very very bright if a little narrow. I also use a standard 3v flashing white bike light to be seen by at all angles and a rear red flashing 5 led light. Total consumption including back light is less than 1.5A so it will give a long time of use. I originally had a bottle dynamo system but I prefer this as the drag from a bottle dynamo was not fun plus I can switch out the 3W Cree for when I am on lit roads and only need to be seen! However, I had a bike a long time ago with a hub dynamo and that was superb, very little drag if at all in real terms, it would be brilliant at keeping this charged and probably allow smaller batteries to be use..