30V 10A 110V Precision Variable DC Power Supply to find short to ground(sort of newbe)

[Veraxis]

Was also looking at these **broken link removed** it offers many advantages, you can view the preset voltage, input voltage, output voltage, the preset current, output current, output power, etc. on the output state remind area, you can see that output opens or not, the state of constant voltage and constant current, output is normal or not, the key is locked or not, and the current data groups that is being used. On the setting data interface, you can adjust overvoltage value, overcurrent value, over-power value, data set and LCD brightness. And it's really well calibrated from the factory. Well worth the money.
My only dilemma is that it comes with a step down module and it needs an ac to dc supply to power it. So as it has Input Voltage listed at DC6-40V. Was thinking of getting a dc power supply that would allow me to use it with this contraption.
So I was looking at these **broken link removed** but it's not a linear one it's a switch. So waiting for more great advice. Thanks in advance.

You could do that if you wanted, but it would require a bit more work on your part. I guess I don't know if those modules would be good or not. I'm guessing that you would want to assemble it all into some kind of case so that you don't have live mains wiring out in the open. It's certainly got a nice display, but it wouldn't be as much of a plug-and-play solution.

Also, where do they specify the accuracy of the calibration? I see the resolution ratings for the display, but that doesn't necessarily mean that it will be accurate to 0.01V. It might say 5.00V on the display, but actually be anywhere from 4.75-5.25V in reality if it had, say, a +/- 5% accuracy on the voltage. The current even more so, as it appears to be using fairly generic wire shunts to measure the current, which usually need to be "calibrated" a bit with notches or solder blobs to dial in the resistance to more than about +/- 10%. They could also be using a software calibration, but it's important to make the distinction between precision and accuracy. That said, I don't know that the meters on the pre-built power-supplies are any more accurate than this would be, and the mechanical needle meters on an older supply probably even less so.

I'm also not sure how comfortable I would be with running 12A through those dinky little wire terminals on the two lower current versions. If you were making this into a more permanent bench supply, I might unsolder the terminals and solder some fairly thick wires directly into the board.

The second set of supplies listed are fairly generic switching power supplies. I have used ones like these before, and the quality of these is reasonable aside from the occasional reports of units with bad solder joints or power transistors improperly clamped to the heatsinks. The listing for the DC-DC converter seems to suggest that it is more efficient in the buck mode when it says that "Please ensure that the input voltage is higher than output voltage above 1.1 times," so I would probably recommend going for the 36V version if you decide to go this route (out of stock on that listing, but probably available elsewhere on eBay).

If you have an oscilloscope with one-shot storage, I would also want to carefully characterize it's turn-on, voltage switching, and steady-state behavior for overshoot transients, rise time, and ripple, which are important characteristics in a power supply if you intend to use this for more than just basic short testing. You will probably want to look at these behaviors both for an open-circuit and under load. If you have a non-storage analog scope, you should at least still measure the ripple. You will also want to keep a close eye on the temperatures to make sure those heatsinks aren't getting too hot under load.

 

[gica69]

You could do that if you wanted, but it would require a bit more work on your part. I guess I don't know if those modules would be good or not. I'm guessing that you would want to assemble it all into some kind of case so that you don't have live mains wiring out in the open. It's certainly got a nice display, but it wouldn't be as much of a plug-and-play solution.

Also, where do they specify the accuracy of the calibration? I see the resolution ratings for the display, but that doesn't necessarily mean that it will be accurate to 0.01V. It might say 5.00V on the display, but actually be anywhere from 4.75-5.25V in reality if it had, say, a +/- 5% accuracy on the voltage. The current even more so, as it appears to be using fairly generic wire shunts to measure the current, which usually need to be "calibrated" a bit with notches or solder blobs to dial in the resistance to more than about +/- 10%. They could also be using a software calibration, but it's important to make the distinction between precision and accuracy. That said, I don't know that the meters on the pre-built power-supplies are any more accurate than this would be, and the mechanical needle meters on an older supply probably even less so.

I'm also not sure how comfortable I would be with running 12A through those dinky little wire terminals on the two lower current versions. If you were making this into a more permanent bench supply, I might unsolder the terminals and solder some fairly thick wires directly into the board.

The second set of supplies listed are fairly generic switching power supplies. I have used ones like these before, and the quality of these is reasonable aside from the occasional reports of units with bad solder joints or power transistors improperly clamped to the heatsinks. The listing for the DC-DC converter seems to suggest that it is more efficient in the buck mode when it says that "Please ensure that the input voltage is higher than output voltage above 1.1 times," so I would probably recommend going for the 36V version if you decide to go this route (out of stock on that listing, but probably available elsewhere on eBay).

If you have an oscilloscope with one-shot storage, I would also want to carefully characterize it's turn-on, voltage switching, and steady-state behavior for overshoot transients, rise time, and ripple, which are important characteristics in a power supply if you intend to use this for more than just basic short testing. You will probably want to look at these behaviors both for an open-circuit and under load. If you have a non-storage analog scope, you should at least still measure the ripple. You will also want to keep a close eye on the temperatures to make sure those heatsinks aren't getting too hot under load.

You are ight On the precission and accuracy I was using some Youtube presentatins as reference to the accuracy for a generic cheap Chianese product, and it was stated that it came closer to any other product of that value range when tested against fluke multimeter. Just a thought. As far as the RF noise from the pwer supply and like someone elese mentioned from the unit itself would that be a problem? I am definitely a hobbyist and am willing to learn. But I like to get equipment that won't put me in the poor house but that are practicle, cheap and effective. You were saying the 36v 10A is the practicle one, I think so too I plan to use it for testing only, they have the module at 30v and 12 A also, but do I just need a straightforward power supply with the respective quality wiring soldered to the step down board, or do I need a booster boards also? Will look for a plastic box for containment. Thanks.

 

[Veraxis]

You are ight On the precission and accuracy I was using some Youtube presentatins as reference to the accuracy for a generic cheap Chianese product, and it was stated that it came closer to any other product of that value range when tested against fluke multimeter. Just a thought. As far as the RF noise from the pwer supply and like someone elese mentioned from the unit itself would that be a problem? I am definitely a hobbyist and am willing to learn. But I like to get equipment that won't put me in the poor house but that are practicle, cheap and effective. You were saying the 36v 10A is the practicle one, I think so too I plan to use it for testing only, they have the module at 30v and 12 A also, but do I just need a straightforward power supply with the respective quality wiring soldered to the step down board, or do I need a booster boards also? Will look for a plastic box for containment. Thanks.

It is not clear from the product description if the board is a buck converter only, or a buck/boost converter, but If you get a 36V supply, you should be just fine for a 0-32V supply. That said, I think a 10A supply would be cutting it a bit close. The DC-DC converter board is rated to 384W max, so a 36V * 10A supply would only have a maximum rating of 360W. It is possible that you could overload the switching power supply if you ran the DC-DC converter at full current, so it may be advisable to try and find a 36V supply rated for more than 10A to give you a bit of safety margin. 30V and 12A wouldn't work either, as that would again be 360W max. The DC-DC converter is the portion with the controlled current limiting, so your AC-DC switching PSU should have a higher power rating than it.

As for RF noise, between the AC-DC switching PSU and the DC-DC switching converter, this thing would probably be a nightmare in terms of RF noise, but you have to ask yourself if you ever realistically plan on building RF circuits. Putting it in a metal box might shield more of the RF noise than a plastic one, but obviously cost is a major factor here. For most normal circuits and for short testing like you are planning, it shouldn't be a problem, but as I suggested, you will want to carefully characterize it's behavior to make sure there isn't any excessive ripple or any transients which might cause issues. There are a lot of unknowns here, so it may not be as simple as just connecting the two together and using it straight away.

In terms of cost, though, $30 for the DC-DC converter, probably another $25-30 for the 36V supply, and however much else for the case and all the little extras like banana plug posts, etc., and I doubt that you are necessarily saving any money over a pre-built unit. The benefit will be the satisfaction of having made your own power supply.

 

[gica69]

Found a 480w 36V power supplyfor $35 Ripple & Noise (max 240mVp-p) Input voltahe 85-135 I assume I can connect to AC 110V regular plug right?
**broken link removed**
What's the best way to limit the rf noise when building this, in layman's terms terms please. Read somewhere about ceramic caps form line to ground 0.01mf>
I don't plan to build anything just using it for shorts testing and in other cases to get variable power to test stuff in case I am missing the power cords or ac adapters. I would buy the aforementioned one at 30V 10A but I really like the options on this one might not need them, I don't know but I assume that having the advance settings is rather unique, a least for a newbie like myself. A pro such as yourself is probably laughing about it and I don't blame you I am the same when it comes to body work and car repair, like to limit cost and buy the strictly necessary rather than the flashy gadgets and tools.
https://ka7oei.blogspot.com/2012/12/reducing-switching-supply-racket-rf.html interesting article about reducing rf noise on what I need. I just need to understand it first.

 

[spec]

Found a 480w 36V power supplyfor $35 Ripple & Noise (max 240mVp-p) Input voltahe 85-135 I assume I can connect to AC 110V regular plug right?
**broken link removed**
What's the best way to limit the rf noise when building this, in layman's terms terms please. Read somewhere about ceramic caps form line to ground 0.01mf>
I don't plan to build anything just using it for shorts testing and in other cases to get variable power to test stuff in case I am missing the power cords or ac adapters. I would buy the aforementioned one at 30V 10A but I really like the options on this one might not need them, I don't know but I assume that having the advance settings is rather unique, a least for a newbie like myself. A pro such as yourself is probably laughing about it and I don't blame you I am the same when it comes to body work and car repair, like to limit cost and buy the strictly necessary rather than the flashy gadgets and tools.
https://ka7oei.blogspot.com/2012/12/reducing-switching-supply-racket-rf.html interesting article about reducing rf noise on what I need. I just need to understand it first.

Hi G69,

Go for the 0V to 30V, 0A to 10A linear variable power supply- why mess about with anything else?

I gather that you are put off by the seeming complexity, but those power supplies are dead simple to use: just plug the power supply in to your mains, set the output volts to whatever you want and the current to whatever maximum current you want and that is that. You can even use the power supply as an an automobile battery charger if you ever need to.

By the way, if you think that the current setting forces that current through the load, that is not correct. The current setting is just the maximum current that the power supply will supply.

For example if you set the output volts to 12V and the output current to 10A and connected a 6 Ohm resistor across the output terminals of the power supply, only 12V/6 Ohms = 2 Amps would flow (just the same as a 24 Watt bulb). If you subsequently shorted out the terminals of the power supply, only 10 Amps would flow and the power supply would not be damaged.

Just think of the power supply as an adjustable voltage battery.

spec

 

[gica69]

Hi G69,

Go for the 0V to 30V, 0A to 10A linear variable power supply- why mess about with anything else?

I gather that you are put off by the seeming complexity, but those power supplies are dead simple to use: just plug the power supply in to your mains, set the output volts to whatever you want and the current to whatever maximum current you want and that is that. You can even use the power supply as an an automobile battery charger if you ever need to.

By the way, if you think that the current setting forces that current through the load, that is not correct. The current setting is just the maximum current that the power supply will supply.

For example if you set the output volts to 12V and the output current to 10A and connected a 6 Ohm resistor across the output terminals of the power supply, only 12V/6 Ohms = 2 Amps would flow (just the same as a 24 Watt bulb). If you subsequently shorted out the terminals of the power supply, only 10 Amps would flow and the power supply would not be damaged.

Just think of the power supply as an adjustable voltage battery.

spec

Yes it does make more sense than to complicate my life building that other stuff even though that display is really appealing and innovative , and I want it just for electronic testing in particular(well for starters) to pinpoint shorts that I cannot detect by measuring components.

 

[Veraxis]

I know it seems like I've been playing both sides of the issue, but personally I kind of agree with Spec that for what you plan to use it for, it may be easier to just buy a prebuilt unit. Building your own power supply is a good learning exercise, but it is a major project and not to be taken lightly. A nice-looking display is all well and good, but at the end of the day I don't really know what I would use it for. A power supply is generally a pretty utilitarian thing as far as test equipment goes.

To answer your question, though, yes, that 36V switcher is rated in the description for 110V mains. 480W would be reasonable margin. You would connect the live, neutral, and ground wires of a normal AC cord to the lugs marked L,N, and with the ground symbol. You may want to crimp some fork terminals to the ends onto the ends of the mains lead rather than just clamping the wires so that you can get a good connection and so you don't risk having any whiskers or other issues.

Spec's point about current setting is a good one, and I find that this is a common misconception about power supplies. The value for current should be thought of as being a limit for the maximum of how much current can flow more than a setting of how much current will flow. In that sense, something like a wall wart PSU might be rated 5V, 1A, will output at 5V, but the current will be variable. I would think of it as being 5V and up to 1A.

As for RF shielding, I would say don't worry about it. RF noise and EMI suppression is a massive and fairly complex topic. Basically it comes down to careful filtering on the inputs and outputs, and using shielding to block any energy that radiates into the air as radio waves.

The 30V 10A bench supply should be fine. They are simple to use and I imagine that once you are used to using it you will start reaching for it as your first choice of power source when testing things instead of wall adapters or batteries.

 

[gica69]

I found this unit that has an issue and want know if it's worth spending money on it to repair and use? It doesn't respond to the controls. **broken link removed**

 

[MikeMl]

Not at $95 for a pile of parts.

 

[Veraxis]

I found this unit that has an issue and want know if it's worth spending money on it to repair and use? It doesn't respond to the controls. **broken link removed**

There's no real benefit to buying a fixer-upper for a power supply, and especially not at that price. For all anyone knows, just about anything could be wrong with that unit. I would keep looking.

The only reason I buy non-working equipment is if I can get a good deal on some very expensive piece of equipment that would otherwise be way out of my price range and has no cheaper alternatives, or if I know EXACTLY what is wrong with it and think I can fix it easily.