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Advice on Relays

Advice on Relays

Postby Eoghan » Tue Aug 17, 2010 12:16 am

Hi Guys.
Just wondering if somebody could advise me. I haven't used a relay before and while I understand what and why I need one I find myself a little confused as to which one I should get to power my laser. Up until now I have been using the adafruit motorshield and powering my laser from one of the motor ports using Waltermos Voltage stepdown schematic.
At the moment I am playing with Milz's excellent LCD sketch (forum/viewtopic.php?f=9&t=1968) and want to power my laser from one of the analog pins. I know that they can handle a max of 40 mA and as I use the green laser sold in the David shop I need 300 mA hence the need for a relay. Am I right in thinking I can use an analog pin as a digital out, in collusion with walters schematic and a relay ? What are the potential pitfalls ?
I have recently discovered this company (http://radionics.rs-online.com/web/) and as they are based only 20 mins away and have excellent service I would like to purchase from them. Could some kind soul possibly take a look at their site and suggest a good relay to get ? It would be much appreciated ! As an aside they also have a range of stepper motors and gearboxes. Anyone have an opinion on these ?
Again much thanks for any help !
Eoghan
Eoghan
 
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Location: Dublin, Ireland

Re: Advice on Relays

Postby WalterMo » Wed Aug 18, 2010 9:30 am

Hi Eoghan,
It's not necessary to use a relay to switch a 300mA laser by the Arduino. Take a look on Gunter's circuit diagram:
http://www.david-laserscanner.com/wiki/ ... re_project

or here on mine:
viewtopic.php?p=5505#p5505

If you still want to use a relay, look on Khalid Khattak's hand sketch (Aug.15th) :
viewtopic.php?f=6&t=1999&start=45

A suitable stepping motor should be this one:
http://radionics.rs-online.com/web/sear ... &R=4328267
The six – wire type can be used in the uni- or bipolar mode.

But don't forget, you need an additional gear for a very fine laser pan.

Walter
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Re: Advice on Relays

Postby Eoghan » Wed Aug 18, 2010 5:37 pm

Hi WalterMo,
Thanks for getting back to me. I spent some time studying Yesterday and came to the same conclusion. I'm going to go down the BS170 Mosfet route.

In terms of the stepper motor I have decided not to buy from Radionics this time. I had hoped to find one compatible with this gearbox http://radionics.rs-online.com/web/sear ... &R=0718919
but when I checked with their technical staff they said they didn't have anything that would couple with it.
With any amount of steppers lying around here my attempts to date at getting a good gearing solution have been dissapointing to say the least ! :(

Back to the drawing board ! At this point I am willing to spend some money to solve the precision problem once and for all. I really want to be able to do reliable panel-less scanning.
Cheers
Eoghan
Eoghan
 
Posts: 21
Joined: Thu Feb 11, 2010 3:31 pm
Location: Dublin, Ireland

Re: Advice on Relays

Postby WalterMo » Wed Aug 18, 2010 7:03 pm

Regarding a stepping motor with an attached gear:
Have you already taken a look to Mattia's collection:
viewtopic.php?f=9&t=1993&p=12334#p12334

Walter
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Re: Advice on Relays

Postby Eoghan » Thu Aug 19, 2010 2:15 am

Hi Walter.
Indeed I have looked at Mathia's post and was about to go down that route until I checked Radionics again.
After many, many hours of trawling through the net, checking datasheets, scratching my head and pulling my hair out, it seems the technical person I spoke to was misinformed.
I've decided to order this Motor,

http://radionics.rs-online.com/web/sear ... &x=36&y=14

with this gear box

http://radionics.rs-online.com/web/sear ... 9&x=20&y=9

and this adaptor kit

http://radionics.rs-online.com/web/sear ... &x=16&y=13

It's proving quite expensive so I really hope I am making the right decision. I am going to place my order in the Morning.

Cheers
Eoghan
Eoghan
 
Posts: 21
Joined: Thu Feb 11, 2010 3:31 pm
Location: Dublin, Ireland


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