The DSKY kits come with battery packs for power, holding 6 AA batteries for a total of 9 volts. However, I want the DSKY units in the Command Module to run off of the DC busses (“Main Bus A” or “Main Bus B”). The DC busses will be 12 volts, so I’ll need to convert the power to 9 volts.
I bought these inexpensive “voltage reducer” kits off of eBay, but it turns out they’re just ordinary 7809-based 9-volt power supplies, but without a transformer. In fact, the input is a 4-diode bridge rectifier, so it doesn’t matter how the input leads are connected. The important thing is that they output 9 volts.
They did not come with instructions, but the circuit board was screen-printed on the component side with all the component locations and values so construction was simple. It even came with a heat sink for the 7809 that soldered into the board prior to mounting the regulator, so it not only held it in place, it kept it cool while soldering. I tested both supplies with a 12-volt input and checked the output – both of them hovered right around 8.95 volts, which is good for the DSKY units. That’s another thing down!