Dangerous Prototypes Open Source Hardware

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Messages - madworm

1

Project logs / Re: DirtyPCB IKEA Samtid mood-light upgrade

August 30, 2014, 03:24:32 pm

I've added the link. I wonder why I didn't add it in the first place...

2

Project logs / DirtyPCB IKEA Samtid mood-light upgrade

August 29, 2014, 01:08:22 pm

Just wanting to share one of my latest projects, made possible by DirtyPCBs. I got a lot of good boards (actually 2 designs) and saved 25$ using this service. Very nice.

It's a simple thing, just a micro (ATmega168) + a bunch of WS2812B LEDs. Main purpose: more colours :-)

[attachment=3]

It's meant to fit nicely into IKEA Samtid lamps, runs with 5V DC and takes up to 2.75A. The control module is removable, so one doesn't have to rip the lamp apart every time you change code. I used microMaTch connectors, as they're somewhat low profile,  at least compared to standard headers, and provide quite good mechanical support.

[attachment=1]
[attachment=2]

The most intricate part of the circuit is a 1-ch level-shifter / bus isolator (google AN97055). I felt I needed it to avoid feeding parasitic power via input clamping diodes of the WS2812B when the whole board is powered by the programming adapter only (main 5V power supply disconnected).

[attachment=0]

Finally, a short video: http://http://www.youtube.com/watch?v=2TPGtW_iQ8U

All design files + code are available via my blog. Hardware might be found on Tindie (search for IKEA).

3

General discussion / What's going on with IteadStudio forum?

April 18, 2012, 06:58:26 am

Does anybody know what the heck is wrong with their forum admins? 10.000 spam posts and no reaction to emails, not even using their shop to contact them works.

Heck, I've even sent them pointers to a few simple to implement patches for phpbb3 to cut down the spam posters.

So far I haven't seen any sloppiness concerning order fulfillment (mostly PCBs), but to me the state of their 'support' forum is a bad omen. If that doesn't change I'm thinking about redirecting future orders to other shops.

4

General discussion / Re: More ITead Mystery PCBs

February 17, 2012, 01:16:46 pm

In my last order I got yet another 'Foca V2.1'... and this black thing. Whatever it is. I wish there was a way to find out where my boards went.



Maybe we should start a Flickr group for this as well ;-)

Done:

5

Client software / Re: OLS signal display component

December 30, 2011, 03:50:50 am

I like it. Cursor snapping is nice and showing frequency/period is great.

Some easy method to show time differences between cursors would be helpful as well. Ideally also with keyboard shortcuts to mark the relevant 2 cursors. The cursors labels are now managed perfectly!

Would it be possible to also remove suppressed channels (nice) from the list completely?

P.S. does the 'demo' support zooming at all? I can't seem to do that.

Edit: seems +/- works, but double-clicking not. Odd.

It would also be nice to use the mouse-wheel for horizontal scrolling (maybe Alt + mouse-wheel). Currently it is used for vertical scrolling only (as far as I know).

6

Open Bench Logic Sniffer / Re: Something you might find useful too [OLS add-on PCB]

October 31, 2011, 01:22:54 am

[quote author="rsdio"]Photo?[/quote]

As I've already got the 'bigger' one in front of me (which can do the same thing if only half-populated), I didn't have the smaller boards made. It looks like this. The design files are part of its bigger brother's.

Here's what the front side looks like (gerber):

7

Open Bench Logic Sniffer / Re: Something you might find useful too [OLS add-on PCB]

October 30, 2011, 12:41:37 am

Unfortunately the coupling between the channels is quite strong. A 100k pull-down is much too weak to kill the crosstalk. I looked at the waveforms on my scope, saw typical RC discharge signals, but was too lazy to use the information any further. I think I could've calculated some rough value for the input capacitance of the pins + wire, knowing the pull-down resistor. Assuming the floating channel gets charged up by a connected channel via some inter-channel capacitance (mainly the wires I guess). It seems with the current setup only 'strong' pull-X resistors are good enough. Using individually shielded probes and GND guard tracks on the PCB would be helpful as well I guess.

Personally I think I will get 4k and 10k resistor networks. And if I should come across a device that can't handle moderate pull-X resistors, I'll curse it and look for a big hammer.

8

Open Bench Logic Sniffer / Re: Something you might find useful too [OLS add-on PCB]

October 29, 2011, 06:34:41 pm

Not yet ;-)

9

Open Bench Logic Sniffer / Re: Something you might find useful too [OLS add-on PCB]

October 27, 2011, 08:20:35 pm

As the pull-down variant with 10k resistors seems to work all the time, I've created a board with just that option and nothing else. Board size (width) and part cost are cut down to roughly 50%, which is nice too ;-)

10

Open Bench Logic Sniffer / Re: Something you might find useful too [OLS add-on PCB]

October 25, 2011, 09:06:58 pm

The one test channel I have working with it right now is quite immune to noise/crosstalk using a 4k-ish pull-up with 2.5V. Going to higher voltages makes it better. Activating a 10k pull-down on the channel works best. In that case I haven't seen any rubbish so far. This was tested using test mode and 200MHz sampling rate + RLE.

11

Open Bench Logic Sniffer / Re: Something you might find useful too

October 25, 2011, 04:01:19 pm

Here's the very simple schematic as well.

I added the 1k series resistors for the voltage lines just in case one should accidentally short out the lines by misplacing a jumper. If you don't need/want them just place a blob of solder on the footprint. It is 0603, so the solder bridge should form quite easily.

12

Open Bench Logic Sniffer / Re: Something you might find useful too

October 25, 2011, 03:52:42 pm

For now this will have to do.

[attachment=1] [attachment=0]

The resistors will be replaced by 8-element resistor networks, once I've decided which resistances I'll need.

If there is interest, I have 9 PCBs left over. I have headers/jumpers/power cable as well, but no resistor networks / dip switches. All boards were E-tested, so there shouldn't be any surprises. I'll post a link to gerber files and so forth once the 24h ban of external links is over.

Edit: Bare PCB would be 4.50$ + postage.

13

Open Bench Logic Sniffer / Something you might find useful too [OLS add-on PCB]

October 25, 2011, 01:10:06 pm

Hi,

as everybody else I've had issues with floating input channels picking up noise or signals from adjacent channels. Grounding unused channels does the trick, but these probes like to slip and it can get a bad mess of wires ;-)

To solve this problem (for me at least) permanently I made a little board:

It supports selectable pull-up and pull-down resistors in two groups with selectable pull-up voltage (2.5V, 3.3V, 5.0V). The pull-down resistors are 10k, which seems to work reliably so far. The size of the pull-up resistors that work reliably depends on the selected voltage. 5.0V and 3.3V works OK with 10k, 2.5V needs something close to 4k to suppress picking up signals.

Please don't ask me what this board does to signal integrity or relative channel delays, I don't know.

Once the forum allows me to post images and links, I will do so.