Thread: 9.7 / 31v DC supply

Hiya, newbie here.

I've got an old pen plotter that's missing a supply, so I want to build one. It's strange old thing with a cloverleaf pin power connection, requiring 9.7v DC on one and 31v DC on the other.

As it's not a 'dual supply' in the usual sense of equal +/-, I'm wondering if there's anything I should be aware of in identifying a design. (The output needn't be more than 1 amp.)

As the input voltages are both positive, I'd wondered whether I could simply step down the output of a 32V adaptor I scavenged at a flea market, either resistively or with an active circuit.

Any pointers appreciated.

Unless the load is pretty consistent you will have a difficult time resistively regulating to 9.7 V, and your resistive component will waste a lot of power. You'll be better off finding a suitable regulator. I would think a 10 V regulator would suffice with a caveat.

When you say pen plotter, I am taking it you mean, what we refer to in instrumentation, as a chart recorder or integrator. Can you identify the model and manufacturer? Honeywell perhaps? Leeds And Northrup?

Those supply voltages seem rather odd. Be aware that integrators have signal inputs as well as power inputs. The voltages you mentions seem odd for signal inputs as well, but no more odd than for power supply.

Or maybe by pen plotter you mean something totally different?

EDIT: Man, I should Google terms before I respond sometimes. Pen Plotters and chart recorders are similar devices but rather different in purpose. I'll stand back and let someone who knows what they're talking about comment LOL

Can you give us the make and model of the plotter?

It's a Roland DXY1300, as shown below.
I haven't any schematic / user manuals, so am not sure what the power board is doing.
I'm guessing the 31v drives the stepper motors.

Just use a common 32 volt DC power adapter that some of the the HP printers use for the 31 volt part and a second 9 volt power pack for the 9.7 volt part.

Typical printers and printer power packs are very sloppy on what voltage they actually produce and use. Anything close will typically works.

My old printer had a 40 volt open circuit on the power pack and pulled down to around 28 volts at times when printing and that never bothered it.

40 volt open circuit? Might have been a switched mode supply, many designs require a load to regulate.

I'd go with tcmtech's idea dglp, it might be a little awkward having two supplies for the one power connector but it'd work fine. Your biggest issues is going to make sure you a power supply that can give it enough current, and of course make sure you hook the power up to the right pins =) You should be able to trace that from the power connectors on the board though.

Good luck with that, looks like a solid toy to get to play with.

It was an old transformer type hence the big voltage drop at load.

My last HP printer also runs on 32 volts or there abouts and has a switching supply that stays around 33 - 34 volts with little voltage change regardless of load.
(I played with it one day to see what it could do.)

Yeah, I always keep laptop and printer supplies cause they're usually very nice switch modes, at least from more modern devices.

Thanks for those tips. I happen to have that 32v supply - so maybe it will give me some motion...

As for the pinout, I'm thinking the LM340 gets the 9v side and powers the RAM board. I traced the circuit along the line shown in black through the LM340 to the ribbon connector. Do you reckon I'm right about that?

If your traces are good it seems sound to me. Ground is pretty obvious, just try to follow the 32volt line and see where it ends up.

The LM340 is rated at 1amp maximum regulation current, I'm gonna guess it goes to 5 volts.

If you used a linear regulator from the 32 volts supply. To drop it down to 9 volts you'd need to dissipate a theroetical maximum of 23 watts of power, that's toasty but not too bad, well within the realm of a well heatsinked linear regulator, but that's wasting TONS of power from the 32V supply which may not even already have enough to drive the steppers alone. I'd definitely use a separate 9V supply for the 9V side. Or a switch mode regulator to buck down to 9V

Be careful if you use two different power supplies though, switch them on via a power strip at the same time, there's no telling what would happen if it only get 32V with no 9V control power, or vice versa.

hrmm I dunno then, I found a reference on the net to a C317, it is ALSO a linear regulator. See if you can trace any of the stepper motor leads back to the power source as you said that's pretty much gonna be a no brainer that it's the 32V line they go to.

You can guesstimate the current for each supply by looking at the size of the fuses.