Got a 12v gel Cell, need 3.3,5,12,32 volts

HD,

Cheap & simple? Assuming you have the original AC driven power supply, just use an automotive power inverter to get from 12 VDC to 120 VAC. Or, a UPS, in which case the battery is included

-- Joe

HD,

The '12v' is just to run motors; it can come straight from the battery, accuracy is not important. The 32V is for the tuner (are you REALLY using the RF input or output?). A '555 driving a voltage quadrupler can get you there, if you can't make do with video/audio I/O ports only. It may have a powersupply spec of 5 mA, but it's unlikely to require that much.

As for the 3.3 and 5V, you want a DC/DC converter (unisolated is fine) that will handle that... either a dual converter or, if you pay attention to sequencing (relatively easy, there's logic inputs on the converter) two single converters like S7BA-06E2ALG, available at DigiKey.

Sadly, these DC/DC converters are only easily available in surface- mount soldering packages... that's where the big market is. Making a wiring harness will be inconvenient.

Um, ok, you win, but I forgot one more...

small

inverter plus original ps too big for the case it has to fit.

of HD,

ally

Are you sure? A 100W inverter, which is more than you need, is pretty small. Just pretend it is part of the gel-cell.

-- Joe

Yup, too big. Have to fit the cell, a wireless video rxvr, an lcd display, and the tivo mb and ethernet card in; there's not even quite enough room for the original ps.

I have looked and think I could build an oscillator and a voltage tripler circuit and then use an adjustable regulator for the 32v (do they come with that range?); and could just run a big pair of 5v and 3.3v regulators, but am not sure what to do about getting a nice smooth 12v from a nominal 12v gel cell.

A lm317 works up to 40v input. I think the LM338 is identical but is rated for 5A. Hell, you can even make a 1.8v reg out of one. Stuff 4 in there and you done. But I would use a switcher for the 3.3 and 5v stuff. What about a mini-itx supply

Cheers

ir of HD,

tually

lay,

th

But the 12v is just for the motors?

Ditch all and use a laptop?

th

You do NOT need to regulate the 32v; the use of this supply is in the RF tuner, to run voltage-controlled oscillators, and it has its own regulation in the tuner (to match the temperature coefficient of the VVC diodes). Since the Series 2 has only NTSC capability, it can't tune broadcast TV this year anyhow; why bother? At most, put a zener diode there. Most three-terminal regulators aren't workable unless it actually draws more than a milliamp of current (or you have to add loads to satisfy the regulator).

If you're cramped for space, you must use DC/DC converters to make the 3.3V and 5V; a linear regulator on 12V input giving 3.3V at 4A will dissipate 35W; that requires a near-infinite heatsink for most single-chip regulators. The 5V regulator will lose power, too.