1
\$\begingroup\$

I'm wanting to start my own lab at home so that I can learn things faster than uni teaches (we're not allowed into labs unless we're in our own lab).

A friend said that I'd be better off getting a power supply than a function generator, since I'm a first/second year elec student because he thought they'd be cheaper, but there's only about $50 difference between the two.

I'm actually wondering whether it would be a good idea to get the Rigol DG-1022, and to supply a dc source, I set the frequency as close to zero as possible. Of course, electricity is dangerous; while I'm cool with blowing an LED or op-amp, I'm not at all happy to assume that a mock dc supply is actually direct current, without first checking if this is safe.

Wondering what you think? I'm not just asking about safety, if you've got other comments, I'm happy to hear them.

\$\endgroup\$
  • \$\begingroup\$ You want to use a function gen to power a circuit. Function gens probably dont have a lot of current. That would mean you would be VERY limited in terms of what you can actually "power". Get a power supply. \$\endgroup\$ – efox29 May 6 '15 at 12:06
7
\$\begingroup\$

No, that won't work.

You could use fixed voltage supplies (AC adapters, wall warts) for most power supply purposes - just understand that your circuits are living dangerously if the supplies aren't current limited, so be careful and double-check your connections - until you can afford an adjustable PSU.

One option is to make one of your first projects an adjustable PSU with current limiting (using an LM317 and a heatsink) powered by an AC adaptor, perhaps a 19V one from an old laptop. It'll teach you about proper heatsinking!

So I'd still go for the function generator as a first purchase (assuming you already have a multimeter!) but use other arrangements to supply power.

\$\endgroup\$
4
\$\begingroup\$

The function generator you are referring to is an arbitrary waveform generator. You can actually punch in a DC signal and live with that.

The specs on the rigol site states that the maximum peak to peak output voltage for channel 1, that is the stiffest, is 10V on a load of 50\$\Omega\$. Assuming the output is ground referenced you have some 5V on 50\$\Omega\$, i.e. 100mA. That is a ridiculously low current for any project this side of turning on an LED. For most projects you will need a dual power supply, sometimes you will need dual power supply plus another positive voltage for digital circuitry, and the signal generator can't help that. 5V is also quite a low voltage if you want to make any decent audio circuit or anything more than some Watts powerful, maybe a stepper driver or whatever.

A signal generator as a power source is definitely a bad idea, you should really consider getting a decent bench power supply. You could also use a wall wart or something like that, that is much cheaper, but I advise against it. You will blow things up and having a current limited, nice stiff 'n steady supply is something you should not skip over. Plus you can use your laptop as a signal generator through its audio output: it's a kinda hacked solution but it's much better than using a signal generator as PSU and I think it is also better to have a nice PSU and a hacked signal generator than the opposite thing.

\$\endgroup\$
  • \$\begingroup\$ you gotta blow a few things up though! \$\endgroup\$ – Brian Drummond May 6 '15 at 15:59
  • \$\begingroup\$ aaaand that's easier with a 100+W bench psu :P \$\endgroup\$ – Vladimir Cravero May 6 '15 at 16:01
2
\$\begingroup\$

If you are only powering low wattage circuits then a function generator can work. I've used them to generate an AC output (like the low voltage output of a transformer) and fed that into a bridge rectifier and smoothing capacitor to power small circuits.

Most function generators will have at least 50 ohms in series with the output and might produce up to 10Vp-p (hand waving alert) so for a moderate load they will work. If you need more than a couple of watts then buy/build a power supply.

\$\endgroup\$
  • \$\begingroup\$ Maybe the phantom downvoter would be brave enough to explain the downvote? \$\endgroup\$ – Andy aka May 6 '15 at 13:26
  • \$\begingroup\$ Can't explain the downvote but I've definitely used an arb for very low power AC circuits. Especially low voltage energy harvesting applications to mimic the output of a transformer. In the poster's case, this is probably a solution for when they're a bit more experienced. \$\endgroup\$ – scld May 6 '15 at 14:10
  • \$\begingroup\$ Upvoted to compensate. \$\endgroup\$ – Brian Drummond May 6 '15 at 16:00
  • \$\begingroup\$ Upvoted because the answer is right. \$\endgroup\$ – Vladimir Cravero May 6 '15 at 16:01
0
\$\begingroup\$

If you want simple and relatively good power supply, you could get yourself an old computer power supply, you will have 5 and 12 volts with good stability, and invest your money in a signal generator(or a scope..or both). It is not hard to create a variable power supply with an lm317 circuit or something which is actually a good project for a novice :) the rigol scope like a ds1054z is only 399 and you will learn a lot, you have cheap signal generators for about 20-25 $ on ebay, just be aware that they are CHEAP, and their signals are not that well formed(which you could investigate with your scope), but it does get you started.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.