Monday, 24 December 2012

Getting my process sorted

Got a bit more time yesterday to build a couple more mixers based of the PCB I made. I am definitely a convert to PCB making as although it takes a good while to make, etch and drill the PCB's when they are done it takes no time at all to assemble them with the components. I've redesigned the board for these to accept phono sockets so after xmas I'll make some of these and possibly try and sell some...I am designing a larger more unusual mixer (more details soon) which is my main idea at the moment.

Thursday, 20 December 2012

Making PCB's..thinking of manufacturing a few bits

So this week I've been experimenting making PCB's using a great freeware package for windows ExpressPCB

I'm using the toner transfer method, laser printing onto glossy paper and then heat transfering the toner onto the copper clad board (ironing the back of the paper on the hottest setting!) I'm then soaking off the paper and etching the boards using Ferric Chloride. Here's a board thats the result of this process.

The board above is for a simple 4 - 1 passive mono mixer which is based on the ones I've made for my CMOS synth stuff. I just wanted something relatively simple to make to get to grips with making the pcb's. Below is the resulting prototype a TINY mixer.

And another shot of her getting tested...

So I plan to make a couple of these for friends and maybe some more for myself, I realised that this board could also be built up with full size pots and audio connectors (jack/phono etc) and stuck in an enclosure so I am going to release a pdf of the board for if people wanted to build there own but I need to do a bit of documentation first. I may do a few boards and offer then for sale. I have more plans for PCB making though and have a few more ideas for small unique things I can make and maybe stay tuned!

Sunday, 9 December 2012

The Missing usb otg

I've been playing with some old nokia tablets (thats right not phones!) I've recently picked up a nokia n800 and an n810 for the retro handheld collection...(I think I need a display cabinet soon...) The n810 is great and actually has many uses for me day to day. I've been away this week and its made a good hotel wifi browser, great note taker  document tweaker with its nice hardware thumboard, and a useful link/transfer device when I needed to get some large audio files off my zoom recorders sd card and into my phone for a bit of on the fly editing. As a transfer device the n810 is very useful as it has 2gig of built in storage as well as an sd card slot....sort of....its a MINI sd slot (not micro) and amazingly I had a micro sd to mini sd adapter from an old phone. This means you can drag stuff off a card and back onto another card although I just did some big bluetooth transfers.

Anyway I was aware that with a USB on the go (otg) cable you can actually connect stuff to the 810 with the 810 acting as host...I hacked together a cable today and got this working (albeit a bit limited) it seems to only work for pendrives but for me thats really useful. I've been playing with powering usb hubs to try and get harddrives running to it but no luck as yet!

To make a USB otg cable you basically have to cut 2 cables in half one that has the micro b connection for the 810 and one that has a femal usb socket. Each cable end should have 4 wires, red, black, green and white and also a bare wire earth sleave wrapped round the other wires. Firstly you have to connect these wire to each other matching the colours and also connecting the earth wire. Then the slightly tricky bit is that the micro b end needs to be opened up (I carved the plastic back off the connector carefully using a razorblade). Once you have exposed the connections to the micro b socket you should discover you have one pin that is unconnected. (this is pin 4 and a lot of tutorials on making these just say to connect "pin 4" to earth...I think it easier to just find the only unconnected pin as it is ALWAYS pin 4 that is unconnected). So then with all the connections visible you want to solder a small wire to the unconnected pin and the other end to the edge of the metal socket housing therefore connecting pin 4 to earth. MAKE SURE that you now only use this for usb otg type operations as when you connect this cable it will want to put the device into host mode.

Anyway, I'll continue to tinker with the n810 and any more useful stuff will be posted.