-5 to +5v from 0 to 5v signal & single +5v supply

Discussion in 'The Projects Forum' started by IraqiGeek, Dec 26, 2012.

  1. IraqiGeek

    Thread Starter New Member

    Dec 25, 2012
    Hi all,

    I am trying to do more or less the same thing that fxmech was, but want to do it (-5v to +5v from 0 to +5V, gain of 2 and offset of -5v) using three LM828 charge pumps (two in series to generate -10V per the datasheet, and a third to get +10) and a LM358 opamp instead of the TL082 used in the mentioned thread.

    I'm good with digital circuit design, but know very little about analog circuits. Tried to install LTSpice, but can't figure how to find the LM828 or LM358, or how to add those components to LTSpice for that matter.

    What I want to do is make an arduino shield that uses the TDA1543 dual 16-bit DAC, to generate a -5 to +5v signal using the arduino +5V (USB) supply. The purpose is to drive those ebay galvos with enough precision to make a small laser cutter/sintering printer.
  2. nightcrawler218

    New Member

    Dec 24, 2012
  3. IraqiGeek

    Thread Starter New Member

    Dec 25, 2012
    Ummm, I'm pretty sure I dont want to clamp the signal. What I need is an amplifier with a gain of 2 all while offsetting the signal by -5v.

    This way, a 0 sent to the DAC will give -5V, 32768 will give 0, and 65535 will give +5v.

    In the thread I mentioned, Wookie already gave a solution, but his was based on using the +/-24v supply of the galvos, and using a different opamp. I tried to comment on that same thread first, but the forum denied the comment because the thread was old. So, I opened this thread.

    I'd like to do it using the +5v supply from the arduino only, this way the "DAC shield" would be pretty generic and independent of an external supply.
  4. SgtWookie


    Jul 17, 2007
    I received your E-mail. Thank you for your explanation, and providing the link to the previous thread that was so similar to your requirement. This makes it much easier on me.

    I am in the middle of a construction project, and am expecting the work crew to arrive in the next few minutes, and that will keep me occupied for the rest of the day. I'll try to get back to you later, perhaps this evening.

    But quickly, attached is LM358.zip.
    It contains:
    LM358.sub - copy to C:\Program Files (x86)\LTC\LTspiceIV\lib\sub
    LM358.asy - copy to C:\Program Files (x86)\LTC\LTspiceIV\lib\sym\Opamps
    If you are using a 32-bit Windows, then omit the (x86) from the Program Files path.
    After the two files are in place, you can then close and re-start LTSpice, and you'll find the LM358 opamp in the list of Opamps after selecting Component (AND gate) from the LTSpice menu bar.

    If you can, I suggest using a better opamp than the LM358. Of course, I don't know what kind of opamps you can obtain in Iraq, but the LM358 is a very old design, and there are a huge number of newer opamps, many of which would be a better choice.
  5. IraqiGeek

    Thread Starter New Member

    Dec 25, 2012

    First, thanks for the quick reply and for all the info/help.

    Second, I'm live in Portugal, hence I have access to pretty much every component that's available on Mouser, DigiKey, Farnell, etc. The LM358 was merely a cheap part I came across on ebay. So, if you have any opamps (or other components) in mind that would suit the application better, please do suggest them.

    The main objective is to keep the shield I'm designing as low cost as reasonably possible while also making it independent of external supplies.

    As I said, I'm more of a digital guy, and my knowledge of analog circuits is very limited.