I think you have your battery symbol backwards in your schematic… Just to make sure others don’t connect it up wrong.

Posted at 3:23 pm on Oct 30th, 2008 by anon

Wouldn’t it have been better to leave PB0/1 disconnected for ICSP?

Posted at 3:29 pm on Oct 30th, 2008 by pokey

Why so many components? Iirc, you can leave off almost half of it (you’ll need sw changes tho’):

1. There’s a good amount of ADC and power saving possibilities in the Tiny13. Leave out both transistors, connect the resistor+photo-transistor to an ADC-pin of the uC (and the ground or vcc of that schematic to another pin, to make sure no current flows when it’s not necessary) and you’re done,

2. Why the resistors? Iirc, the Tiny13s GPIO will emit 20mA or so at max. The current limiting is there, just use it :)

3. You can even leave out the photo-transistor :) Can’t find a link right now, but it’s possible to use a LED as a photo-detector.

Total of parts left (perhaps I’m missing a resistor): the battery, the 2 leds and the uC.

And who said leaving out stuff was only a merit in writing? :)

Posted at 3:34 pm on Oct 30th, 2008 by Sprite_tm

@sprite_tm Here’s your link: http://hackaday.com/2006/02/21/low-cost-sensing-and-communication-with-an-led/

Now are you going to build it or what? ;)

Posted at 3:40 pm on Oct 30th, 2008 by Eliot Phillips

Heh, I’m tempted. Tell you what, if I have some spare time this week, I’ll build and document it if you’ll show it on hackaday. Deal? :P

Posted at 4:32 pm on Oct 30th, 2008 by Sprite_tm

@pokey: perhaps he wanted hardware PWM? (OC0A/OC0B)
@sprite_tm: I don’t think an almost empty schematic would be worthy on hackaday.
Heck, there are already too many of these little projects on hackaday.

Posted at 4:37 pm on Oct 30th, 2008 by DarkFader

You still need resistors to drive an LED from a microcontroller pin. Their maximum output is near 20ma, which means you shouldn’t exceed that…the microcontroller won’t actually limit it.

Posted at 5:37 pm on Oct 30th, 2008 by macegr

mad scientist projects are boring :(
what is the use of the transistors ?
with a tiny 45 you can take 40ma ou of single a output pin and you can connect 2 together, that is 80 ma.
No, you do not need a resistor to drive a led (try it !) except to spare your battery life, anyway you can do pwm if you want.

Posted at 8:26 pm on Oct 30th, 2008 by timour

@sprite_tm Those sound like good ideas/improvements, if you want to discuss your design further hit me up at nick@hackaday.com

Posted at 8:52 pm on Oct 30th, 2008 by Nick Caiello

Actually, I got the no-resistor idea for the original from a post on LadyAda’s forums, stating the AVR chips do have regulated output.

(BTW, thanks to hack-a-day for linking my Instructable. Twice! :D )

Posted at 10:22 am on Oct 31st, 2008 by SolidSilver

these “little projects” can go a long way towards communication and networking of ideas.

Look at the ideas for refinements brought about by posting this circuit.

There are no “little projects”.

Posted at 3:47 am on Nov 1st, 2008 by strider_mt2k

i think this simple circuit is useful for me as a reference as i’m new to these stuff, thanks!

Posted at 1:06 am on Nov 2nd, 2008 by han