Looking for a decent adjustable bench power supply...
Kevin Wood
Posts: 1,266
Hello all.
I'm looking for a not-too-expensive (maybe $250 max, prefer $125...) adjustable bench power supply. I would like something that outputs up to about 30Vdc, and maybe 5A. Multiple outputs would be nice, but not necessary.
Can anybody recommend anything? Even if it's not close to my specs, if you are using something that you would recommend, I'll take a look.
Thanks.
I'm looking for a not-too-expensive (maybe $250 max, prefer $125...) adjustable bench power supply. I would like something that outputs up to about 30Vdc, and maybe 5A. Multiple outputs would be nice, but not necessary.
Can anybody recommend anything? Even if it's not close to my specs, if you are using something that you would recommend, I'll take a look.
Thanks.
Comments
Whatever you do, stay away from the one pictured below (made in China under various private labels). It had good specs, and the price was right, but it has two fatal flaws: 1) the output voltage is unstable (noisy pot?), and 2) when you turn it off, the output voltage glitches high. On top of that, a peek inside the case is just plain scary.
You get what you pay for. Stick with known brands like Extech or Agilent (HP). If you can't afford to buy new, eBay can be counted on as a source of used brand-name test equipment at reasonable prices.
-Phil
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'Still some PropSTICK Kit bare PCBs left!
Don't know about the noise factor but the voltage have been stable enough for my 6502 board (Replica 1).
I used this one for the 24x24 LED display (www.brielcomputers.com/phpBB2/viewtopic.php?t=212).
I did have problems on the 24x24 board before I added the by pass caps but otherwise it's been doing great...
From left to right, -12V, -5V, GND, 3.3V, 5V, 12V.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Living on the planet Earth might be expensive but it includes a free trip around the sun every year...
Experience level:
[noparse][[/noparse] ] Let's connect the motor to pin 1, it's a 6V motor so it should be fine.
[noparse][[/noparse] ] OK, I got my resistors hooked up with the LEDs.
[noparse][[/noparse]X] I got the Motor hooked up with the H-bridge and the 555 is supplying the PWM.
[noparse][[/noparse] ] Now, if I can only program the BOE-BOT to interface with he Flux Capacitor.
[noparse][[/noparse] ] I dream in SX28 assembler...
/Bamse
http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&ProdID=12528
Hey, that is a slick idea! Mounting the banana plug jacks right in case of the PC power supply. Somewhere I have a bag full of those jacks and now I finally found a use for them.
Thanks for posting the picture!
Robert
Hewlett Packard/Agilent, BK Precision, Sorensen, even Radio Shack/Micronta are some good ones to look for.
HP (now Agilent) in particular is big in power supplies and there are usually a lot of them available in many configurations.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- Rick
Sure, with audio stages, one might need 30 VDC. But with solid state and instrumentation 3.3 VDC, 5 VDC, and 12 VDC are just fine. A computer power supply with load resistors properly in place should do fine. And consider having two supplies - one for digital bench work and another for analog instrumentation.
One might consider using +/- 12 VDC for op amps. But the switcher power supply typical to computers may cause trouble with op amps by replicating the noise from the switching supply.
Try to locate a Ham swap meet in your area and you may find someone that can easily supply you with a good piece of second hand equipment. There was a ton of old HP equipment that was sold for salvage in the 1980s.
An even better option to get started, a pair of 12volt gel cells can provide you with noiseless power a lot cheaper than filtering AC. You can even save quite a bit of money by building your own charger.
Everyone thinks they have to have expensive lithium batteries, but it isn't true for bench work. The gel cells can be much cheaper [noparse][[/noparse]though larger] and provide many years of service.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
PLEASE CONSIDER the following:
Do you want a quickly operational black box solution or the knowledge included therein?······
Post Edited (Kramer) : 7/11/2008 4:39:05 PM GMT
One adjustable supply: 0-30Volt 0-3Amp
Two fixed supplys: 12V 500mA; 5V 500mA.
They run about $170.
http://www.extech.com/instrument/products/310_399/382203.html
They also have a digital model that is slight more expensive (I have no experience with the digital model).
Bean.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
"A government big enough to give you everything you want, is big enough to take away everything you·have."·· Thomas Jefferson
"It is our choices, Harry, that show what we truly are, far more than our abilities."·Dumbledore from Harry Potter
www.iElectronicDesigns.com
·
-Phil
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'Still some PropSTICK Kit bare PCBs left!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Just as an fyi, here are a few that I found after posting...
www.tucker.com/java/jsp/product_partno1671A_invid5294_condN.htm
www.testequity.com/products/1607/
It is good to have a few decent SLA batteries around. I have a 12v and a 6V SLA that I keep set aside for bench testing. They help when I want to use a circuit away from the bench.
I often find that it is handy to have a decent adjustable supply though. In particular I used it in place of the battery when working on circuits for mobile robots. Having the adjustable supply helps test the point where the battery low signal can trip. It also helped in another circuit testing an analog battery monitor for use on another robot.
Robert
Phil,
Just how bad was that thing inside? Did you get any pictures?
I think I have almost the same model. I think that Mastek is the manufacturer and they will put whatever name on it you want. I have one similar to your unit with the exception mine has RED and GREEN 7-segment LED displays. It has dual 0-30v 3A out and a 5v 3a fixed out. The controls are not as precise as I'd like but so far it seems to work ok and the display looks nice. I don't think I'd trust it for precision work but for a general purpose PS so far so good.
The note about the high voltage spikes when you turn it off is a bit disturbing and I'll have to watch out for that. What were you using to find them?
Robert
- The ability to·store settings.·Having 2·or 3 buttons·to select·configurations you have stored previously.
-·The ability to lock·settings.·Some units have such a smooth control knobs that is too easy to change settings inadvertently.
- The unit should·show Voltage and Maximum Allowed Current on the display BEFORE you actually press the GO button!
Although you may consider these features standard there are many lab power supplies that do not have them.
A·brand I liked was Kenwood. However they do not sell power supplies anymore.
Regarding chinese units, I have used one of these (although not the one in the picture), branded as ISO-TECH,·and was a very good unit. So don't rule out chinese products without trying them.
·
I noticed the meter readings going high when I turned off the power, so I checked with a scope and, sure enough, the glitches are real. 'Sorry: no photos of the guts, though.
Kevin,
One thing to check for in the specs is how fine a control you have over the current limiting. Most projects require only tens of milliamps. If the current control starts at 250mA, as it does on the B+K unit (5% of 5A), you won't derive much protection from it.
-Phil
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'Still some PropSTICK Kit bare PCBs left!
If I need regulation, linear regulators seem to be quite adequate. They can be shunted with a 2N3055 to output multiple amps. In fact, by using components such as these, I am really bench testing what I'd use in the final design. But I just have build up these things as standard bench modules.
The only thing the linear regulators won't easily do, is go down to 0 volts.
Wouldn't the voltage going high on a shut down indicate a coil is being used for filtering and the field collapses? Or is this from the transformer's field collapse?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
PLEASE CONSIDER the following:
Do you want a quickly operational black box solution or the knowledge included therein?······
Edward