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91  Forum 2005-2010 (read only) / Frequently-Asked Questions / Peer review on: February 18, 2010, 08:14:48 am
I'm getting close to sending off my first fab-project - I'd be greatful if anyone could give it the once-over to see if I've missed anything  smiley

It's very simple - basically a generic LED driver/sequencer for model projects. There are 8 outputs, each using a ULN2803 darlington for additional power.

The Atmega is fed 5v through a LDO regulator, but the LED supply is taken from the unregulated side - this allows running off 4.5v if necessary without losing a large drop over the reg, but still using the reg to provide polarity reversal protection.

There is space for a series resistor in each output on the board for simple deployments - where more than one LED per output is needed, they can be added at the LED end and the on-board res can be omitted or bypassed by shorting the jumper pads on the bottom side.

There are 0.1u SMD decoupling caps under the 168, and a 1u tant for the regulator - is that sufficient?

2 inputs are brought out to JP1 to allow for 4 jumper selectable options. I've also brought out an ICSP jumper but may be doing the programming in my Arduino. Seemed wise to include it though.

Routing was significantly tidied up after autorouting.

Circuit:
http://i113.photobucket.com/albums/n202/ants-nest/Misc/Driver.png

PCB
http://i113.photobucket.com/albums/n202/ants-nest/Misc/DriverPCB.png

Any feedback greatly received!
Cheers
92  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Mega168 flavours - what's the difference? on: December 09, 2009, 03:11:16 pm
Don - thanks fo the info!

JCL - unfortunately the datasheet linked to is the wrong one - it's for the 164

Cheers
93  Forum 2005-2010 (read only) / Frequently-Asked Questions / Mega168 flavours - what's the difference? on: December 08, 2009, 07:48:47 am
Browsing the Rapid website here

http://www.rapidonline.com/Electronic-Components/Integrated-Circuits/Atmel-Microcontrollers/ATmega-8-bit-AVR-Microcontrollers/77086

they seem to have several 28 pin DIP versions of the 168 listed:
ATMEGA168V-10PU 8BIT MICRO 16K
ATMEGA168-20PU 8-BIT MICRO 16K
ATMEGA168P-20PU 8 BIT MICRO 1K

The first 2 are nearly half the price of the last one... Does anyone know what the V/P & PU signify. Also the last one says 1K...?

The datasheet for the last one seems to actually point to the 164 so that's not much help.

Cheers
94  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Resonator vs Xtal on: November 24, 2009, 03:31:24 pm
No, accurate timing is not required, and there's no serial capability, so it looks like I'm fine with a resonator, saving a few pence and sq mm

Cheers
95  Forum 2005-2010 (read only) / Frequently-Asked Questions / Resonator vs Xtal on: November 24, 2009, 08:23:04 am
After a successful prototype I'm putting together a short production run of a standalone project - just wondering if there are any huge benefits of using a crystal over a resonator & cap combo? I'm looking at keeping it simple & cheap as poss...

Cheers
96  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Getting started - which chip to use? on: November 23, 2009, 07:37:03 am
I can recommend Mike at http://earthshinedesign.co.uk/ - he stocks both the 168 and 328 bootloaded enabled.

97  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Unregulated battery power ? on: September 01, 2009, 06:46:31 am
It's for some display lighting in a model - it needs to be portable since there will be no mains at the venue, and it only needs to last a few hours on a charge so I'm not too worried about long term efficiency.

Cheers
98  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Unregulated battery power ? on: August 28, 2009, 05:09:33 am
Was going to be using NiMh - maybe it would be safer to stick to 3 cells then if there's a chance of 4 being over voltage after a full charge. I didn't really want to add the overheads of regulator circuitry if possible...
99  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Unregulated battery power ? on: August 27, 2009, 09:16:37 am
@jcl - no, I'll be driving 96 leds (4 groups of 24 at 10ma a piece) via PWM through various sequencing & fading patterns. Although they could potentially be on all at the same time the average will be much less, but still considerably more than the Mega.

@dogsop - interesting - I was banking on the 1.2v / cell and assumed that would not be high enough to run through a 5v reg...
100  Forum 2005-2010 (read only) / Frequently-Asked Questions / Unregulated battery power ? on: August 27, 2009, 06:34:58 am
I'm building a project that needs to run off battery power - pretty basic, just an Atmega328 and a whole bunch of LEDs with suitible drivers.

Ideally I'd just like to use 4 C or D cell rechargeables and run the whole thing off the 4.8v directly - will the 328 be happy with that?

Is there anything else I need to take into account? I'm not really worried about what happens when the batteries go flat - as long as there's no damage!

Cheers
101  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Deploying Arduino project cheaply? on: May 14, 2009, 11:59:22 am
Thanks guys - they all look like the sort of thing I need!
102  Forum 2005-2010 (read only) / Frequently-Asked Questions / Deploying Arduino project cheaply? on: May 14, 2009, 06:46:50 am
Hi,

I''ve recently bought a Duemilanove to develop a lighting controller for a model. Ultimately I want to make this a permenent part of the model so don't really want to use the Due, but rather I'm looking for a 'minimalist' cheap runtime option that I can just drop the programmed AT chip into, but doesn't have all the comms hardware.

Does such a thing exist?

Also if I just buy a new AT328 chip, am I right in thinking I need to get the bootloader onto it somehow before I can upload my code through the Due?

Cheers
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