I just realized you were trying to power charging circuitry, not charge the batteries themselves. Why can the chargers not be connected in parallel if they are separate units?
The idea of the lm317 is that they are cheap. And wouldn't a 1:1 transformer only regulate voltage, and give different currents for batteries that have different charge levels? Another option would be to use an ATX supply, which can supply many amps at 5 volts. To compensate for the voltage drop, you could add a power transistor on the output. this way you would only need an lm317, a power transistor, and 1 or two resistors per circuit. A nice safety feature and convenience would be a comparator on each charger to isolate the battery. Also, what voltage are the batteries, and what voltage do the commercial chargers charge them with?
I am not sure if this exists, but some ribbon cable with solid conductors that would be good for breadboarding data buses and such would be great. Some dip switches that take up less breadboard space by just having a pin that sticks into a breadboard power or ground rail would also be great, but I don't think those exist.
Ye,s it would dissipate a lot of power with a twenty-nine volt drop. For this design you would need a low voltage high current supply with a bit of heat sinking.
Here is a schematic. You will have to adjust the resistor to get the desired current, and make sure it has a sufficient wattage. It is also worth noting that no matter the output voltage, your supply will always have to supply the same amperage as the output. So your cell can draw 1a at 2v and your 5.2v supply will still have a 1 amp load. The lm317's also have a thermal overload shutoff so they will not burn out. I believe it may also be possible to emit the resistor because they have a 1 or 1.5 amp current limit built in, but you would have to check the datasheet. if the datasheet says it has over current protection just make the resistor 0 ohms. Multiple circuits will let you charge several batteries at the same time on the same supply. [attachment=0]
As far as charging batteries I do not know very much, however you may be able to use one lm317 current limiter circuit per battery, all attached to a 5.2 volt supply that has enough amperage to supply two amps per circuit continuously. One regulator per circuit is enough for charging at one amp, you will need two in parallel for two amps.
I just bought ten 630 tie point breadboards for about $3.50 each on eBay, free shipping. I will have the father of all breadboards, at least once they arrive. The mother of all breadboards has 26.
I personally like the lab tool idea best. It doesn't limit people very much, and they can make something actually useful. Plus, I've wanted to make about seven pieces of test equipment but stopped that to make a 7400 contest entry.
i think it would be cool to have us make a specific thing and tell us nothing about how to make it. Or, as I said, we could have a transistor contest, analog contest, retro computer contest (my personal favorite, and there are a lot of them out there), 555 contest, or date code before the 80's contest.
You already told me about that. Same guy, different thread. I will most likely be satisfied with whatever substitute contest they come up with, unless it involves programming. I know enough to get by, but logic is what I do.
