"Sip N Puff"-controlled laser... Thanks for looking!

Discussion in 'The Projects Forum' started by likearock111, Jul 16, 2007.

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  1. likearock111

    Thread Starter New Member

    Aug 9, 2006
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    Hi, all!

    I'm working on a for-fun project for a surgeon friend of mine. He trains residents in laparoscopic surgery and needs a way of directing his students where to cut/cauterize on an LCD video monitor, and his hands are already completely tied up with instruments. Therefore, I'm working on a head-mounted laser pointer controlled by a sip and puff switch.

    I've got the sip and puff switch (World Magnetics was really nice to send me a free sample!), and I've got a green laser module (the DPSS-5) on order. According to the specs available, it runs off of 3V, and, assuming that it's a pretty typical module, it probably requires about 200 mA (based on other comparable lasers I saw).

    The sip and puff switch is of the normally-open, momentary contact variety. I really need latched control of the laser, and I found the EDE2208 that seemed pretty good for that task. I know you can use T or JK flip-flops to do this, but this IC seemed much simpler (albeit 8x bigger than I really need) and has debouncing included.

    This leads me to my next hurdle: I need to give the laser 3V and up to, say, 300 mA. I had planned on putting a 2:3 voltage divider on the 5V latched output of the EDE2208 to get a node at 3V wrt GND, and then put a buffer op-amp out of that node that could source 300 mA @ 3V directly to the laser. After several days of searching Digikey/Jameco/etc., I have not been able to find an op-amp that can do this.

    Does anyone know of an op-amp that could be powered by a 9V battery that can source 300 mA? Also, I have thought about using a non-latching relay (5V coil voltage, no voltage divider needed)... should I go that route? I have also considered just putting three or four 100mA-capable op-amp buffers in parallel, but I've never tried it and don't even know if this would work. Any other project suggestions would also be greatly appreciated.

    Thank you!
     
    Last edited by a moderator: Jun 28, 2010
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Take a look at National Semiconductors' LM134/LM234/LM334 series devices. They're 3-terminal current sources, and you can do a lot of things with them - plenty of application hints are in the docs. An ultra-simple current regulator can be made by using just the device and one external resistor.

    Note that it has a temperature coefficient, which can be canceled out by adding another resistor and one diode.

    Download the .PDF datasheet from either National or alldatasheet.com
     
  3. likearock111

    Thread Starter New Member

    Aug 9, 2006
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    Thanks for the input!

    I just stumbled upon the Burr-Brown/TI REG104, which has an active-high enable pin that should be able to control power to the laser using the output of the EDE2208 (I think). I think I'll give this a try.

    PS: Are there better/cheaper ways to get a basic 2-sided PCB made than by using ExpressPCB? I think that they charge $50 for three small boards.
     
    Last edited by a moderator: Jun 28, 2010
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