bench power

Discussion in 'General Electronics Chat' started by duxbuz, Apr 12, 2014.

  1. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
  2. Mike33

    AAC Fanatic!

    Feb 4, 2005
    349
    25
    Yes and no, Dux...it will be fine for entry-level things; you can run it to an LM317 circuit to create a variable supply. You might need to heatsink the 317!!! It will certainly put out more current than you're ever likely to use, too! So for 'getting started', it is good....it's like a CB power supply that I used to use :eek:) Many get going using just a 9V or so wall wart, so this is a step up.

    OTOH, for a bit more money you could probably find a variable supply. I spent about $100 US, and got a 30V, 5A variable supply that will run everything from a portable air compressor down to 5V TTL, ha ha. It is well-regulated, too, so is not noisy. That might be 'too good' for what you want to do, however.

    You can overcome the low cost of the one you're looking at by using a regulator as I described above and filtering it well so it doesn't 'buzz' on audio circuits. I think it would be a sensible purchase as long as you're ok with building a little regulator "side board" for it.
     
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,752
    760
    It will be OK. But we dunno the noise level on tht thing.

    And for logic circuits u still need 5V regulators.
     
  4. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
    Ok what's a 9v wall wart

    I want small as possible really
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    For small, I'd look at the plug-in adapters for USB charging. They're only about 1" square and give over 1A at 5V DC. This won't serve all your needs - 12V would be more versatile - but there is an awful lot you can do at 5V.

    A plain old transformer-based adapter (= wall wart) is another option. You can find them for free because they are obsolete, and you should have no trouble finding one rated to 12V and 0.5-1A, for instance. Some have a rectifier built in, but you could make your own if you have only an AC-AC transformer. To use a wall wart, you'll want a filter capacitor and a voltage regulator (e.g.. LM317).

    Next up is the laptop power brick, which can deliver about 19V and 4A or so. Not so small but a lot of power for the size, weigh and cost.
     
  6. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,532
    1,251
    Your link is for something to run automotive accessories on a bench, not adjustable, unknown noise and regulation performance, and will need external regulation for 5V and 9V work.

    A wall wart is a small, plug-in power supply, usually black, like what used to come with calculators. A lot of them were 9 to 12 V. Now days most are 5V with a USB cable.

    If you shop around at electronic surplus sites you'll find a bunch of them, including universal types with a selector switch for 3, 5, 9, 12, etc. Around $20 US. Radio Shack had a nice one if they're still around.

    ak
     
  7. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
  8. Evil Lurker

    Member

    Aug 25, 2011
    117
    23
  9. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,532
    1,251
    Last edited: Apr 13, 2014
  10. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
  11. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,752
    760
    I think the one above will have poor load regulation.
    No load voltage will be high and as loaded voltage will drop.
     
  12. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,752
    760
    You can use these with a proper transformer and bridge plus a smoothing cap quite well.
    I use them
     
  13. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
    Would they still be no good if I had voltage regulator on my circuits?

    thanks
     
  14. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,752
    760
    They will be quite good.

    U do not need a regulator. It itself is a regulator. You can get any voltage from 1.25 to 30V by varying the blue pot on it.
    Of course the input voltage must be at least greater than 5V than the required output

    with 5V input you will get 1.25V with good regulation.

    If you need 5V out, input should be at least around 10V.

    Read the listing.

    It has short circuit protection too. Only way you can destroy it with a hammer :D
    And ya with reverse input. I know cause I blew one with reverse input :eek:
    it literally blew.

    I showed u one with only voltage adjust. They also come with CC too. output current adjustable. Just do a buck converter with CV & CC

    Before connecting the circuit to it, u would need to measure the output with voltmeter and adjust the pot to ur required voltage. And it will stay at that upto 2A or 3A. Maximum current is in the listing
     
    Last edited: Apr 13, 2014
  15. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,503
    380
    hi dux,
    Have you considered adding to that 13.5Vpsu, a 7809 [+9v] regulator followed by a 7805 [+5v] regulator. ?
    A simple heatsink would hold the 7809 and 7805 regulators.

    The +5V will be OK for most MCU and Logic work, the +9V is useful for OPA work.

    http://www.bitsbox.co.uk/index.php?main_page=index&cPath=140_171

    28p each UK.
     
  16. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,532
    1,251
  17. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
  18. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,532
    1,251
    Yes, either of those would be a good front end for something with its own regulator. Remember to deal with the heat in the 7805. In round numbers, a TO-220 package is good for under 2 watts in free air before whatever is inside burns up. Use a heatsink.

    And, the tab of a 7805 is connected to the center pin, GND. Don't let it bump things.

    ak
     
  19. duxbuz

    Thread Starter Member

    Feb 23, 2014
    133
    0
    In regards to heat.

    I don't currently use a heat sink on 7805 when using just a 9v battery.

    So should I opt for the lesser mA one (300mA) ?

    Would the 300mA allow me to run the 7805 without a heat sink?

    Thanks
     
  20. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,503
    380
Loading...