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Author Topic: Possible to wire a pen laser to the axon2?  (Read 2356 times)

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Offline GrooveHolmesTopic starter

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Possible to wire a pen laser to the axon2?
« on: March 06, 2011, 04:14:21 PM »
The dollar store near me sells these cheap $3 made in China laser pointers I use to exercise my cats.



I took one apart over the weekend and noticed is has really low power requirements and has an easy to hack push button switch. The batteries are LR44 watch batteries, which according to public documentation provides 1.5V @ 150mA (times 3, for 3 batteries in series), so 4.5V @450mA.

http://en.wikipedia.org/wiki/LR44_battery

So the 450mA far exceeds the recommended 20mA limit per pin, but would there be a way to use lower the amps with some resistors (dimming the laser, which is fine it's almost too bright anyway!), or provide an easy alternate power solution to allow the laser to be turned on/off by the axon?

:) Muchos!
The difference between the student and the master, is that the master knows what he does not know.

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Re: Possible to wire a pen laser to the axon2?
« Reply #1 on: March 06, 2011, 05:07:54 PM »
Replace the button (which is a switch) with a MOSFET (which is also a switch).

Your Axon then controls the switch by sending a signal to the gait pin of the MOSFET.

Offline GrooveHolmesTopic starter

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Re: Possible to wire a pen laser to the axon2?
« Reply #2 on: March 06, 2011, 05:25:30 PM »
This wouldnt' draw too much power?
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Re: Possible to wire a pen laser to the axon2?
« Reply #3 on: March 06, 2011, 05:27:45 PM »
The power from the Axon I/O pin to the MOSFET will be under 1mA (not a problem).

It's kind of like a tiny little button connected to a huge power grid. Simply pushing that little button controls a huge amount of power.

Offline GrooveHolmesTopic starter

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Re: Possible to wire a pen laser to the axon2?
« Reply #4 on: March 06, 2011, 05:50:46 PM »
So the answer, is no, it can't be powered directly from the Axon, but using a MOSFET and seperate (original power supply), it can be turned on/off using an Axon IO port?
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Re: Possible to wire a pen laser to the axon2?
« Reply #5 on: March 06, 2011, 05:54:05 PM »
It can be powered from the Axon power bus (tons of power), but not from the ATmega640 I/O pin (almost no power).

Offline waltr

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Re: Possible to wire a pen laser to the axon2?
« Reply #6 on: March 06, 2011, 08:34:45 PM »
Quote
1.5V @ 150mA (times 3, for 3 batteries in series), so 4.5V @450mA.

http://en.wikipedia.org/wiki/LR44_battery
Look at that battery info again!

It is Not 1.5V @ 150mA but 1.5V @ 150mA-hour
which is the battery capacity.

Offline Soeren

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Re: Possible to wire a pen laser to the axon2?
« Reply #7 on: March 07, 2011, 12:21:45 AM »
Hi,

I took one apart over the weekend and noticed is has really low power requirements and has an easy to hack push button switch. The batteries are LR44 watch batteries, which according to public documentation provides 1.5V @ 150mA (times 3, for 3 batteries in series), so 4.5V @450mA.
A typical LASER diode will take around (loosely) 40mA, but some have a relatively limited range from the point where they "LASE" and to the point where they die.

So, even if it's a cheap LASER pointer, build this circuit and let it live.

Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline BANE

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Re: Possible to wire a pen laser to the axon2?
« Reply #8 on: March 07, 2011, 11:19:29 AM »
i actually have a similar cheap laser pointer 4.5v @ 15mA (i tested the amperage with my multimeter) and need to make that exact circuit.  I have everything except a BC337, but i do have a 2N4401 from radio shack http://www.radioshack.com/product/index.jsp?productId=2062615.  will this transistor be equivalent?

Offline Soeren

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Re: Possible to wire a pen laser to the axon2?
« Reply #9 on: March 07, 2011, 12:39:58 PM »
Hi,

i actually have a similar cheap laser pointer 4.5v @ 15mA (i tested the amperage with my multimeter) and need to make that exact circuit.  I have everything except a BC337, but i do have a 2N4401 from radio shack.  will this transistor be equivalent?
Sure.
Just found a data sheet for it. It's not a very good transistor (hope you got it cheap), but fine in this circuit. The pinout is the mirror image of the BC337, but I didn't post the PCB anyway, so just have in mind that the pin out is E, B, C when you hold it so you can read the markings on it.

In case anyone else wonders, the 2N2222 is a close US equivalent to the BC337, but with a drain under 100mA, even BC547 or 2N3904 will do.

Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

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Re: Possible to wire a pen laser to the axon2?
« Reply #10 on: March 07, 2011, 12:55:59 PM »
This is what I use:
http://www.sparkfun.com/products/8654

Maybe $10 more than a home-made version, but it's well designed and compact.

Offline BANE

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Re: Possible to wire a pen laser to the axon2?
« Reply #11 on: March 07, 2011, 01:17:49 PM »
Quote
(hope you got it cheap)
15pk for $2.59 :P  but hey it just has to work

Quote
This is what I use:
http://www.sparkfun.com/products/8654
$18.95 just seems a little pricey for a $1.50 laser pointer; just saying :P

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Re: Possible to wire a pen laser to the axon2?
« Reply #12 on: March 07, 2011, 01:50:41 PM »
$18.95 just seems a little pricey for a $1.50 laser pointer; just saying :P
That is, of course, if these things are worthless to you:
- your time
- size of the device
- quality/reliability of finished product
- TTL electronics built in

 :P

Offline Soeren

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Re: Possible to wire a pen laser to the axon2?
« Reply #13 on: March 09, 2011, 12:11:07 AM »
Hi,

$18.95 just seems a little pricey for a $1.50 laser pointer; just saying :P
That is, of course, if these things are worthless to you:
- your time
- size of the device
- quality/reliability of finished product
- TTL electronics built in
Some actually do this stuff to:
- Fill their time in a giving way
- Know what's inside
- Get known quality, rather than assembled in the SEAN
- Pride in making it themselves
- Save a good load of money in the process

 8)  :P
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives


Offline BANE

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Re: Possible to wire a pen laser to the axon2?
« Reply #15 on: March 09, 2011, 06:52:10 AM »
sorry guys, i didnt mean to set you guys off.  If you a $60 laser pointer a $20 driver seems acceptable.  I have $300 wheel chair motors controlled by $125 sabertooth.  Would you recommend a newby robot builder buying an Axon II for the $50 robot when all he really needs is the Atmega8?  If you have a $225000 farrari would't you want a $60000 engine?  Vise versa, if you have a el-cheapo satern would you put the farrari engine in it?  

dont get me wrong, i agree the points listed whole heartedly, i just have a problem paying that for a dollar store item.  However, buy a higher quality laser and i'm a happy camper ;D  

Offline Soeren

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Re: Possible to wire a pen laser to the axon2?
« Reply #16 on: March 09, 2011, 08:48:08 AM »
Hi,

sorry guys, i didnt mean to set you guys off.
No problem, it's just friendly teasing :)


Vise versa, if you have a el-cheapo satern would you put the farrari engine in it?  
Yeah, that would be a worthy project if you had both  ;D
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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