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May 18, 2024, 12:37:42 am


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Messages - Andy Brown

General discussion / Re: Cheap PCB production
June 24, 2016, 01:41:38 pm
Looks like a good first design you've got there. The one thing that does stand out to me is that C3 is rather close to that pin header. If C3 really is the diameter indicated in the drawing then you may find yourself bending the leads away a little to move it away from the end of the header.
General discussion / Re: Cheap PCB production
June 18, 2016, 06:34:58 am
Have you remembered to add screw holes either for feet or for mounting into a case?
General discussion / Re: Cheap PCB production
June 16, 2016, 02:04:39 pm
For a 2 layer board most houses will just require (top layer) GTL, GTO, GTS and (bottom layer) (GBL, GBO, GBS) as well as the TXT drill file. They'll also want the board outline to appear on one of the layers. During the design I have the board outline as a 2 mil trace on a separate mechanical layer and then during the export I use an option to include that mechanical layer on all exported files. All the houses seem to be happy with that.

Before sending anything anywhere I preview it in the free ViewPlot 1.5. The author of ViewPlot seems to want us to use and pay for a much more expensive 2.0 version now. Don't bother. 1.5 is perfect for our needs. Just load up each side individually to preview what it'll look like. e.g. First load up GTL, GTO, GTS and TXT and zoom/scroll around to check it (it helps to change which layer is in focus using the on-screen selection box). Then restart the program and do the same for GBL, GBO, GBS. I've found the odd error like this and it also helps draw attention to crazy routing decisions that are best revisited before you commit to copper.
I've now built a case for Nanocounter. Well, it's more of a shield than a case but it does the job of protecting it from knocks and drops. Check out the article here.

General discussion / Re: Cheap PCB production
June 15, 2016, 01:58:11 pm
Hi Phil,

For 2 layer boards I've tried Seeed, ITead and Elecrow. Quality-wise they're about the same and I wouldn't be surprised at all if they all contracted to the same manufacturer. I settled on ITead because on one order I made a mistake that I only spotted after submitting the design. I emailed them and they contacted the board house and held the order while I submitted corrected Gerbers. Good service like that on a small $20 order deserves to be rewarded so they got my custom from then on.

For 4 layer boards I've tried ITead and PCBWay. The quality of the 4 layer boards is, I think, markedly better than the 2 layer boards when compared at the limit. The drill accuracy is better - they tend to hit closer to the center of the via pad. The solder mask aperture positioning seems to be better as well. When I received my Nanocounter boards back from PCBWay I was very pleasantly suprised to see that the soldermask was intact between the pins on the 0.5mm pitch QFN40 package on every board in the package. Those little slivers of soldermask are only about 3.8mil wide.

4 layer boards are in general a lot more expensive than 2 layers. It's not too bad at 50x50mm but a set of ten 100x100mm will run to about $50 plus shipping, compared to about $11 at Elecrow for the same size in 2 layer format. I've settled on PCBWay for 10x10cm again because of service. I've played email tennis with them asking questions about layer stackup and dielectric characteristics and each time they've quickly answered the questions.
I've got one of those boards. You know they can be had for US$1.98 including shipping on Ali Express. I seriously don't know how these guys can make a profit.
stm32plus C++ library / Re: stm32f103C8 & timers
June 11, 2016, 12:57:05 am
If you look again at the clock tree you'll see that the route through to TIM3 includes an x2 multiplier that's active when the ABP1 prescaler = 1. That's how it gets back to 72MHz when the APB1 clock is 36MHz AND the APB1 prescaler = 1. Does that cover your clocking scenario?

Regarding your timer output. Can I see a little more of your timer setup? In particular what are you using for the initCompare() parameters?
Today I moved the website and forum to a new host because my previous provider has decided to move to hourly billing which would have cost me 500% more per month to operate the site.

If the forum tells you it can't log you in and the message is something like "check your cookie settings" then go to your browser's cookie management options and clear out all cookies with 'andybrown' in the site name. Apologies for the inconvenience.
If it's as simple as converting a range of 700 to 2300 then your formula is:

(value - 700) * 100 / 1600

Use 32 bit integers and do the calculations in the order presented to avoid loss of precision. Also best to constrain your captured value to a range of 700-2300 to avoid under/overflow. Is it that easy do you think?
Now how do I convert the captured pulse width to pwm duty cycle to drive my hbridge

If you know the frequency of the signal being sampled (the input signal) and you do know the frequency of the timer used for the sampling (you choose that in the code) then you also know the number of timer ticks between two rising edges.

Your interrupt triggers on rising and falling edges. The difference in capture values between those two interrupts is the duty cycle, measured in timer ticks as a fraction of the maximum possible, which you have pre-calculated.
Hardware projects / Re: Z820 mobo hack. anyone?
May 07, 2016, 12:19:53 am
A very useful pinout table there. I modified your post to prettify the table to make it more readable, hope you don't mind.
General discussion / Re: Eagle and Kicad
May 04, 2016, 02:10:00 pm
I've been an Altium Designer user for many years and a few years ago I did try Eagle because it's free and it would have been good if people could directly use the designs that I create. Unfortunately I hated Eagle and went back to AD. Maybe I'll try KiCad one day but to be honest AD is so good and I know it so well that it would be difficult. Maybe the free online Altium Circuit Maker would be a better option. If you can live with the 'online' part then you do seem to get all the good bits of AD.
I've just published a detailed review, with two accompanying videos, of the Maximator FPGA development board. This was my first experience with the Altera MAX10 FPGA series, click here to see how I get along.

Quote from: lvoigt on April 20, 2016, 03:09:43 pm
Can anyone help me with determining what temperature sensor is used in Z800 (thermistor) power switch/speaker cable assembly?

Hi, Check out this post further back in the thread.
I recently bought myself a basic studio lighting kit on ebay that included a CFL bulb labelled as 135W.

This seemed like a good opportunity for a 'consumer information' style video so, here it is: