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greg199
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Joined: 03/11/2015
Location: Australia
Posts: 39

Posted: 03:23am 30 Jun 2018

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From time to time over the years I would have liked to own a laboratory power supply when fiddling with low voltage gear (mostly 12V). I'm not an electronics hobbyist at present but may become one now that I'm retired.
I can't remember my previous needs but at the moment I find my 3 different multimeters don't all give the same voltage or current readings when testing items so I wanted a calibrated power supply to test them and know once and for all which are good.

Now I'm planning to buy a power supply and this seems okay....
https://www.jaycar.com.au/0-to-30vdc-0-to-5a-regulated-power-supply/p/MP3840
Any comments on it's reliability, etc or a better alternative ?

Ralph2k6

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Joined: 24/09/2017
Location: Australia
Posts: 129

Posted: 03:39am 30 Jun 2018

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If you check through this section, a while back warpspeed and some others have had joy from some Aliexpress kits.
I think that jaycar one would be fine, just may need to keep eye on output ripple.

My 2c only.

Ralph

greg199
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Joined: 03/11/2015
Location: Australia
Posts: 39

Posted: 05:08am 30 Jun 2018

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Thanks.
The ripple voltage on the Jaycar unit is 1mV and the ripple current is 3mA.
A similar unit from Altronics has a ripple voltage of 200mVp-p so this seemingly very high value plus the fact I can download the manual (and it seems clearly written) from Jaycar but not from Altronics, I'm thinking the Jaycar unit maybe good for me.
I have no idea, mind you, whether a ripple voltage of 1mV and a ripple current of 3mA is good or bad for a power supply. What are your thoughts?

Last question: I'd like to teat myself to an oscilloscope as well so can you suggest a suitable unit to suit my beginner needs? Edited by greg199 2018-07-01

Ralph2k6

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Joined: 24/09/2017
Location: Australia
Posts: 129

Posted: 06:20am 30 Jun 2018

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Others here will know more about bench supplies than me, but that jaycar one does sound well specced.
I bought the DSOshell made by JYEtech. It was a kitset and is pretty good for amateur beginners, depending what you're after.

Ralph

Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 4406

Posted: 07:42am 30 Jun 2018

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If it does what you want, and are happy with the price, I would ask just one question.

Does it come with a service and repair manual with a complete circuit diagram ?

A lot of the stuff coming from China works reasonably well and is certainly well presented.
But if it spits the dummy, you could be in real trouble trying to fix it.

Cheers, �Tony.

wiseguy

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Joined: 21/06/2018
Location: Australia
Posts: 1156

Posted: 02:57am 01 Jul 2018

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Hi Greg, thought I might make a comment or two. When a spec of Ripple says Max 200mV it does not necessarily mean that it will always (or ever) be that value of ripple at the output. However if you draw maximum current from the supply it may become that high, but at low current (say below 50% of rated output) it may me very much lower than this & perhaps even immeasurable (this is not a guarantee just a prediction based on experience).

My suggestion is that a good quality accurate reliable meter (brand name?) will be more invaluable to you long term and if you can afford it a CRO may become your second best friend. A lower spec power supply (low ripple is good) is fine - you can always set the output accurately with your DVM (or and calibrate their internal meter).

Make sure your 3 x meters have good batteries and go visit a colleague or friend to help you check them for accuracy against their meter, maybe one is ok and 2 may be better off binning - some low cost meters have very few adjustments (if any) and you may be just opening a can of worms to try to calibrate them.

For peace of mind, if you google for a cheap precision voltage calibrator some auction sites have various versions for $5 - $40 & you can check your DVM's accuracy (DCV) with one of these - AC accuracy for typical hobbyist use is usually not as important. Consider also obtaining an accurate shunt, say 0.1R @ 5 - 10A and a couple of at least 1% resistors say 47R 4K7 47K and 470K measured accurately and written on a tag to keep in a cupboard for checking your meter's performance from time to time.

In all honesty I have only ever got NATA calibrations on my multimeter when a specific contract calls for it - they are usually very reliable & accurate - just dont mistake volts for amps or ohms when measuring mains.....

If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike

greg199
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Joined: 03/11/2015
Location: Australia
Posts: 39

Posted: 02:32am 02 Jul 2018

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Thanks for the comments.
I purchased the Jaycar MP3840 unit and found that my multimeters agree with the power supply unit +- 20mV on the cheaper multimeters to about +-10mV on the more costly units. The one voltage meter that I was having doubts about reads 0.4V too high. So I'm happy I can rely on the multimeters which vary in price from about $10 to $200.
The manual that came with the MP3840 power supply was incorrect but luckily I could download a correct version - just a pity I had to figure out the manual was incorrect rather than a faulty power supply and then had to write about 1/2 page of corrections on the hardcopy that came in the box.

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