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Your thoughts on what makes a good and versatile bench power supply?

Discussion in 'General Electronics Chat' started by bigal_scorpio, May 15, 2012.

  1. bigal_scorpio

    bigal_scorpio Active Member

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    Hi Jim,

    It just goes to show that not everything newer is better designed! It would be a lot bigger job to change the output drivers in a PSU designed nowadays.

    Makes you proud to be knocking on!

    Al
     
  2. Mr RB

    Mr RB Well-Known Member

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    Nice PSU JimB, I love seeing that reliable old 1960's 70's stuff being saved and re-used. That stuff was made to go forever, not like modern stuff. Even new transformers now have thermal fuses inside the windings and they know those thermal fuses fail after a few years...

    I like the long skinny form factor too, the trouble with all my PSUs is they have big fronts so they take up a lot of shelf space.
     
  3. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    after my BOT project i will do a bench PSU for me my wish list would be

    variable voltage from -15v - +25v
    variable current limit 5mA - 3A
    polarity protection (i think thats what its called)
    nice graphic LCD read out and anologue meters
    pre fixed voltage outputs that were accurate for say 3.3v 5v 12v
    lg
     
  4. dave

    Dave New Member

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  5. JimB

    JimB Super Moderator Most Helpful Member

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    A few comments on your wish list LG

    It is not usual to have a PSU which adjusts through zero between positive and negative voltages.
    Actually, that sounds like a really bad idea.
    A negative voltage is usually on a separate terminal and may be independantly adjusted, or it tracks the positive supply.

    OK

    Mmmm....
    Polarity protection is something usually applied to the load, just in case some idiot connects the power the wrong way round.
    I don't see how this could be built into the PSU.
    (Unless you have the wrong term of course)

    Graphic LCD, sounds a bit overkill. but is it floats your boat...

    How accurate is accurate?
    Surely the 78xx series regulators are accurate enough for most practical purposes.

    Also consider that you may not want to squeeze all this functionality into one box.
    It is often more convenient to have two (or more) power supplies, you may want to leave something running in one location and be working on something else in another location.

    JimB
     
  6. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Polarity protection

    If you look at the LM317 specs, there are two diode that can be added for reverse polarity protection. These prvent destruction of the regulator if an external source is connected to the power supply output.

    + and - outputs from the same knob is very unusual, however I have run into a few HP models that did that. They happened to be called a power supply/amplifier. They were about 3 Amps at 60 V or so, but only had a few KHz bandwidth.

    Something that hasn't been mentioned is 4-quadrant operation. The above had that feature. 4-quadrant means it can operate +V and +I, -V and -I and -V and +I and +V and -I modes.

    Goto www.circuitspecialists.com and type "electronic load" into the search box.

    One of the more ultimate power supplies is the source measure unit. http://www.home.agilent.com/agilent/product.jspx?nid=-33504.0.00&cc=US&lc=eng and www.keithley.com make them.

    Agilent's unit is capable of graphing a current-voltage cure on the front panel.

    Series Operation of identical supplies allows one control to modify both outputs. e.g. One setpoint for voltage and 1 for current.

    Parallel operation of identical supplies allows the current to be doubled.

    Programming: Resistance, front panel, voltage, USB and IEEE-488 are also possible.

    Isolated analog programmability is almost essential because the setpoint voltage is usually applied relative to the positive terminal.

    The ability to program lots of supplies from a single interface helps in ATE situations and lots of times the analog programming is more useful than the digital programming.

    Isolated analog out is yet another feature in some supplies.

    A contact closure that shuts down the power supply is another useful feature. Sometimes it uses a special breaker which can be tripped with a voltage.

    The fancier supplies allow a universal input 90-240 or 90-280 VAC input.

    What was stated earlier was form factor or front panel space. I totally appreciated the ability to get a 1500 W power supply in a 1 Rack unit form factor and universal input.

    Remote sense is mandatory for high current supplies.

    Crowbar for Overvoltage protection

    This gives you an idea of a nice supply. http://www.electro-tech-online.com/custompdfs/2012/05/XG_1700_Datasheet.pdf

    Note that there is the possibility to drive polarity reversal relays and output disconnect relays.

    In my application, these were not available at the time and if they had a constant power mode they would have been more perfect.

    One thing that you don't generally see on a power supply is the power in Watts as a metered value. In my application, this would have been useful as well.

    LG mentioned the ability to set specific voltages such as 0.8, 1.8, 3.3, 5, 12, 15, 24 and custom could be useful.

    So, I've been discussing possible options. It's always nice to start from an unobtainable list and then select. I encourage those to initially discus possible options. Later a vote migh decide on the "best" options.
     
  7. bigal_scorpio

    bigal_scorpio Active Member

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    Hi Mate,

    Thats a cracking idea! Why not have a vote? Get a consensus of what most people want in PSUs.

    Is there any way that someone could put a wish list on here that people could add to at will?

    Keep the opinions coming guys (and gals). Al
     
    Last edited: May 18, 2012
  8. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    how about say a usb connection for logging current drawn etc? AC and DC variable would be ace like a built in Variac, also my (ok dads) signal generator goes from 0v-30v with 4 diff wave forms so it isnt that far from being a PSU kinda anyway so how about having say the option to have square wave and sine wave on a output?? its only a wish list so if it isnt possiable dosnt matter :D
     

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