Help Understanding Operating Specs of Step Up Regulator

Discussion in 'General Electronics Chat' started by djsfantasi, Apr 27, 2015.

  1. djsfantasi

    Thread Starter AAC Fanatic!

    Apr 11, 2010
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    I have ordered a 9V Step-Up Voltage Regulator after destroying a similar variable output device (don't ask and I won't tell). My motivation was that all I needed was 9VDC from 5.2VDC and the variable feature was unnecessary (and made the replacement cost higher).

    In reviewing the specs, I noticed a 1.4A input maximum. I always understood that a device only drew what it needed from a larger, maximum supply current. This is being powered from a PC power supply at 5VDC. The supply is rated at 8A. Is this going to cause a problem? (Note that I hadn't hooked the earlier regulator to this power supply...)

    As a little background, I had something working for years, but when I added a new device (Arduino Mega, drawing an additional 40mA), my system stopped working. That is when the manufacturer of the non-functioning device (an SSC-32 from Robotshop) suggested taking my 5.2VDC input, boosting it to 9VDC, so the mis-performing circuit could successfully regulate it to 5VDC. I thought it was strange (Boost 5V to 9V to regulate it to 5V?!?), but decided to give it a go since the manufacturer said it did not support 5.2VDC input.

    I also suspect that the Mega couldn't talk successfully to the device at 115,200bps (although that speed is supported), so in addition to re-powering my system, I've configured communications to take place at 9,600bps.
    Capture.PNG
    So do you think I am OK with my Boost Regulator? What do I have to look out for?
     
  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    I believe the specification is reflexive of the output current (i.e. the load must draw no more current than that which occasions a regulator input current of 1.4A)...


    That's according to reason!:)
    'Step down' VRs (whether 'switching' or linear) require input EMF greater than their designed (or 'programed') output --- Application of input EMFs less than the (desired) regulator output plus said 'dropout offset' will result in no, low and/or noisy output...

    I think you're 'good to go' --- One caveat though - Please take care to assure that the (boost) regulator's output will never see less than its minimum load Spec! --- HV 'spikes', etc are phenomena that digital systems can live without!:eek:

    The 'underpowered' condition of the VR was probably 'messing with' the RS232 levels as well - It is well worth your while to recheck it at full speed once the system is properly powered:D


    Best regards
    HP
     
    Last edited: Apr 27, 2015
  3. Brownout

    Well-Known Member

    Jan 10, 2012
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    You understood correctly. I think the spec should have said "minimum" input current for the supplied power. Your power supply is more than capable to supply this current.


    I do.
     
    Last edited: Apr 27, 2015
  4. djsfantasi

    Thread Starter AAC Fanatic!

    Apr 11, 2010
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    Thanks for the comment. The company has discounted the replacement and is sending it to me for the cost of shipping alone. Pololu has been great.
     
  5. Brownout

    Well-Known Member

    Jan 10, 2012
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    Let us know how that works out.
     
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