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Bevels
08-18-2009, 01:35 PM
Hi, I have a laser pointer that I disassembled and wired so that I have a ground and a voltage lead coming out the back of it. I want to wire it to the SSC 32 so that I can use a script to turn the laser on and off. Is it possible to do this? If so, how would you recommend going about it because I am worried about burning out the laser. The laser is a standard 3V laser that you get at staples or office depot.

darkback2
08-18-2009, 02:07 PM
I think you need something like the battle switch (http://www.trossenrobotics.com/store/p/5467-BattleSwitch-radio-controlled-10A-relay.aspx). I know that particular one is probably more expensive than your looking for, but that might get you looking in the right direction.

Hope this helps.

DB

DresnerRobotics
08-18-2009, 02:10 PM
Or this, cheaper and smaller: http://www.trossenrobotics.com/store/p/5194-PicoSwitch-Radio-Controlled-Relay.aspx

lnxfergy
08-18-2009, 02:13 PM
Doesn't the SSC-32 have digital outputs? Couldn't you use a simple transistor circuit to switch the load on and off?

-Fergs

jes1510
08-18-2009, 03:39 PM
Yeah I think the outputs can be configured to be simple digital outputs. How much current does the diode need?

Adrenalynn
08-18-2009, 03:58 PM
Sorta. You can do discrete output on any of the 32 channels.

#<ch><lvl><cr>

#0H<cr> would set channel 0 to logic high (+5v) on the signal pin.
#0L<cr> would set channel 0 to logic low (0v) on the signal pin.

The response time is <= 20ms.

To expand on what Fergs wrote -

You should probably use a couple transistors wired in a darlington-pair type circuit. But I wanted to go cheap and easy and drawn in gimp (all I have on this machine) and I know the radio shack part numbers for these - so you get a single Darlington circuit. The "snubber diode" is there to prevent reverse polarity damage. Probably not _required_ on a laser LED circuit, but, meh, put it in. It's like a buck for four of 'em (or a couple bucks for 25 of them if you buy in bulk from someone else) The downside is that these devices are high saturation, so you're going to kick off more heat and draw more power - but it should work fine as drawn... [Note: I'm not the goddess of discreet logic, so feel free all to review and comment!]

All necessary parts are regular stocking items in most Radio Shacks (catalog numbers inc.)

mannyr7
08-18-2009, 06:05 PM
Sorta. You can do discrete output on any of the 32 channels.

#<ch><lvl><cr>

#0H<cr> would set channel 0 to logic high (+5v) on the signal pin.
#0L<cr> would set channel 0 to logic low (0v) on the signal pin.

The response time is <= 20ms.

To expand on what Fergs wrote -

You should probably use a couple transistors wired in a darlington-pair type circuit. But I wanted to go cheap and easy and drawn in gimp (all I have on this machine) and I know the radio shack part numbers for these - so you get a single Darlington circuit. The "snubber diode" is there to prevent reverse polarity damage. Probably not _required_ on a laser LED circuit, but, meh, put it in. It's like a buck for four of 'em (or a couple bucks for 25 of them if you buy in bulk from someone else) The downside is that these devices are high saturation, so you're going to kick off more heat and draw more power - but it should work fine as drawn... [Note: I'm not the goddess of discreet logic, so feel free all to review and comment!]

All necessary parts are regular stocking items in most Radio Shacks (catalog numbers inc.)

You're definitely the goddess of something; +rep from me!

Adrenalynn
08-18-2009, 08:22 PM
:) Thank you! :)

CogswellCogs
08-19-2009, 12:27 PM
I used a spare channel on a ULN2803 driver chip to turn a laser on and off. The chip is basically eight Darlington pairs in a DIP package. It's made to interface logic circuits to drive larger loads (up to 500ma).
Each channel has a suppression diode for inductive loads.

I know you have a laser already, but I was very happy with this device:
http://www.apinex.com/ret2/ltgan.html

It's self contained, has a lens, and runs off 5v. That's a voltage that many circuits already have available.

Adrenalynn
08-19-2009, 12:59 PM
What about Trossen's TTL laser? Nice thing about that TIP Darlington that I posted is that you can build it for less than four dollars. Or pennies if you build a few. And use laser pointers that cost $0.50-$1.50 instead of $30...

Bevels
08-19-2009, 02:31 PM
Where can I find laser pointers for $0.50 to $1.00. Also, do you think that using 5V instead of 3V will burn out the laser?

CogswellCogs
08-19-2009, 03:47 PM
I don't know about your laser, but I burned up a cheap laser pointer trying that exact thing. I remember thinking 'Wow ! That's a huge spark for just 5v". Then, no more laser. Live and learn.

Adrenalynn
08-19-2009, 04:09 PM
I bought these when they had a sale going on - they were on sale for like $.80 a piece when you bought five of them. Doesn't seem to be current. But $1.79 isn't tooo far off. ;) http://www.dealextreme.com/details.dx/sku.22333 They actually do a really decent job.

Measure the current on them and figure out what size resistor you need. They're just glorified LEDs. Pop a resistor in there and your 5v becomes 3v. Resistance isn't always futile. ;)

Sid723
09-07-2009, 01:06 PM
If your digital output is able to provide enough current, you may be able to directly drive the laser from the output. Typically, laser pointers draw about 100 milliamps. By using the circuit below, with a 2 watt, 10ohm resistor (probably from radio shack), it can be done simply. If 1 output cannot supply enough current, you can try two (in parallel) to get the current you need. Just keep the 2 watt resistor away from anything that it may melt. It will get a little warm, depending on how long you leave the laser on.

1472

Adrenalynn
09-07-2009, 02:07 PM
With most of the MC's we typically use, even parallel outputs wouldn't sink enough current. The Arduino likes to crash over ~40mA, for example. The ATTiny I typically use will sink about 33mA.

Toss a twenty cent transistor in there and call it good. ;)

Sid723
09-07-2009, 05:21 PM
In that case, your TIP120 suggestion is the ticket. Although I don't think you will need to put the diode in the back. This is usually for inductive circuit protection (but won't hurt things). The transistor shouldn't get too hot, since you are not using a whole lot of power here.

But, still.. if you want to use the 5 volts from your controller, you can still drop the extra voltage through the 10 ohm, 2 watt resistor. Otherwise, you will have to keep batteries in the laser pointer.

Sid723
09-08-2009, 12:58 AM
OK, so taking the 5 volts from your controller's 5 volt supply, we have this:

1488

I looked up the specs on some laser pointers and they actually draw less current than I originally thought, actually about half (50 milliamps). So this is why I raised the series resistor to 47 ohms. Too much current will also not be good for the laser pointer.