I just posted Multiputs - Controlling 8 inputs using a 74HC595 and 4 wires on Codeshare. Feel free to discuss and make suggestions here.
9 Likes
This took me three days and is the hardest project I’ve built so far. Thanks for the support!
1 Like
@ wbsimms - Nice one. These things can be a challenge to get the timing right.
I’ve just finished a 12x8 outputs and 12x8 inputs board with an on-board STM32F405 using 74HC595 and 74HC165. Took some time but it’s working great now. The output and input scan completes in about 5 seconds, which I think could be improved, but not too bad for 96x2 full register sweeps.
Well done.
1 Like
@ wbsimms - what program will open the readme.md file?
@ Bill_Wyo - .md is a markdown file, so just look for a markdown reader app.
I use Visual Studio with the Web Essentials plugin. It has great markdown support.
Thanks! I’ll be honest and admit that I burned three chips before I got it right. :wall:
What prototyping board are you using for your STM32 development? There seem to be so many options.
Thanks,
Barrett
@ wbsimms - I’m building my own for somethings but occasionally use my Spider or Cobra to prototype, This project uses an ST32F405 and the Cerb firmware (non-commercial) to drive them.
4 Likes
That’s so cool. I’m so jealous. Keep us updated!
1 Like
I manually solder masked, placed and then reflowed using an IR reflow oven. The 74HC595 and '165 needed some TLC as they have 17 pins and are less than 4mm x 5mm in size. If you look carefully you can see some hook-up wire on thru '165s where I missed off a track :-[
Very happy with it now it’s all working though.
1 Like
So now I’ll be up all night reading about solder mask and reflow ovens! Thanks for feeding my learning addiction.
I do think Jason might have meant “Solder paste” not mask - since mask is the bluey stuff on his board protecting the copper layers
What he most likely did was apply paste manually before adding the components and reflowing the board… it’s possible to get stencils made to make that more like a “smear” job rather than a “fine toothpick on each point” job. Huge time saver on a board that size/complexity.
2 Likes
@ Brett -I did. Thanks for spotting that.
@ wbsimms - the grey substance on the SMD solder pads is solder paste with flux. A very thin metal or plastic sheet with holes lasered through it is layered over the board and a thin layer of solder paste is then speed over it. The components are very carefully placed onto the board and then precisely heated so the solder melts and connects the device to the board. The amount of paste used is critical to the success of the operation, in my opinion… 
1 Like
@ wbsimms - Thanks for posting your work. This looks like a good way to extend the capability of a cerbuino bee I have in my garage. The ic you used requires 5V which can come off the cerbuino but I am thinking I will power the switches separately. You mention issues with debouncing, could this signal be damped to eliminate the problem? In my application I just want to get a signal indicating a door has been opened or closed so a delay in the indication is ok.
1 Like
@ Bill_Wyo - Thanks for the support.
I’m thinking I can handle the button bouncing in the code. Just a small sleep (10ms?) at the top of the interrupt handler should handle it. It’s not glorious but should work.
Are you thinking of using a Switch Reed?
http://www.jameco.com/1/1/27611-35-756-bu-magnetic-proximity-reed-switch.html
Are you looking to monitor one door or several? If it’s several, you’ll need the '595. Otherwise, I think you could just use a Switch Reed with a single interrupt handler. It would just be one wire to the controller.
I apologize in advance if my response is super-rookie… I’m really out of my element on most of this. Normally, I wouldn’t make any suggestions or assertions until I’ve prototyped it… Hey, maybe I’ll do that this weekend?
This is all super cool. I spent most of last two nights learning about this. How many of you personally have this equipment? Do you mill and etch your own boards?
1 Like
@ wbsimms - It’s not a difficult to get setup and started as you think.
Eagle (http://www.cadsoftusa.com/) for schematic and PCB design
http://www.DFRobot.com for manufacturing
http://www.SMTStencil.co.uk for the solder patch stencil
and something like this http://www.ebay.co.uk/itm/T962-Infrared-SMD-BGA-IC-Automatic-Reflow-Oven-UKG-/260889172245?pt=UK_Home_Garden_PowerTools_SM&hash=item3cbe34d915 for reflowing.
I’ve only been reflowing my own board for about 6 months although designing then for a good bit longer.
1 Like
I just need a really good and detailed instruction video for the whole process…?
For the Multiputs project or for PCB creation?
For your multiputs project, I am just waiting for you to start selling it.
For the production of your pcbs, I was just wondering if there was a really good video showing the whole process from start to finish…