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91  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: SMD Silkscreens on: February 25, 2010, 01:01:23 pm
Quote
I'm at work behind a difficult web filter, so I can't see the image you posted.
Ha - yeah I know all about that  smiley-sad

Thanks for the tip - I am using Eagle - I just tried the SparkFun cam file which did not produce the extra bits on the silk - so a bit of further poking revealed these were in the bDocu layer.. There was something else on the bottom silk I missed - some polarity indicators that I added to bDocu myself, which is why it was turned on.

I've moved them up to bPlace and all is well. Lesson learned - thanks for the help!

(Incidentally, the sparkfun cam doesn't seem to use the bCream layer at all..)
92  Forum 2005-2010 (read only) / Frequently-Asked Questions / SMD Silkscreens on: February 25, 2010, 12:14:47 pm
Not an Arduino question per se...

I'm just about to send off my first design for PCB fab - but checking over the Gerbers I noticed something odd..

I've got some 1206-package SMD caps and solder-jumpers on the bottom side of the board - they are the only things in the bottom silkscreen layer, but it would appear that the silkscreen ink would actually interfere with the solderability since it directly covers the unmasked parts of the pads.

Here's a simple example



For the caps there'll be a chunk of ink directly under the ends of the cap-chip - this may not be such a problem since the solder will connect the end faces to the pad above/below the ink, but for the case of teh jumper, the semicircles of ink will ack as solder mask exactly where you don't want it.

Surely that's not correct?

Any thoughts?
93  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Peer review on: February 19, 2010, 07:02:34 am
No - there is a solder-jumpable pad on the bottom side of the pcb under each resistor....
94  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Peer review on: February 18, 2010, 02:20:22 pm
Cheers Mike - appreciate your time!
95  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
96  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
97  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
98  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
99  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
100  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.

101  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
102  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...
103  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...
104  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
105  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!
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