serial download cable using old earphones!

[munsta88]

Hi guys!


Im trying to make my own download serial cable atm, and I've got hold of some old broken earphones which i plan to use as the download cable.

The problem is after removing the each of the earphones, I've got 2 wires (1 copper, 1 red) inside left earphone and other right earphone another 2 wires (1 copper, 1 blue). I will be soldering these wires to my 9Pin female connector, but heres the problem....

Im sure the copper will be GND as both contain the same copper wires. BUT which wire (red? blue?) goes to Serial In?out? If i took a random guess and hooked it up. Will the picaxe result in any major damage?


Thanks

 

[hippy]

Get it wrong and you could easily destroy your PICAXE.

The copper wires most likely go to the sleeve of the 3.5mm jack ( as 0V / Earth / Common ), the blue and red will go to tip and ring. Unlike headphones the PICAXE download cable doesn't have 0V on its sleeve but on the tip.

The best way is to use the deatils in the manual for wiring the cable to D-connecto and use a multi-meter to determine which wires are which on the 3.5mm jack.

                                               1/S   2/R   3/T                .---------------.
.----------.   1/S     2/R   3/T           .--------------------.             |               |
|          |---------.-----.-----.       .-|  .--.  .--.  .--.  |   .---------| Serial Out    |
|          |         |     |      \      | |  |  |  |  |  |  |  |   |         |               |
|          |         |     |      /      | |  |  |  |  |  |  |  |   |  .------| Serial In     |
|          |---------^-----^-----'       `-|  |  |  |  |  |  |  |   |  |      |               |
`----------'    |      |      |            `--|  |--|  |--|  |--'   |  |  .---| 0v            |
                |      |      |               `--'  `--'  `--'      |  |  |   |               |
PC RX ----------'      |      |                |     |     |        |  |  |   `---------------'
                       |      |                `-----|-----|--------'  |  |         PICAXE
PC TX -----------------'      |                      |     |  .-----.  |  |
                              |                      }-----|--|     |--'  |
GND --------------------------'                     _|_    |  `-----'     |
                                                   |   |   |    22K       |
                                               10K |   |   |              |
                                                   |_ _|   |              |
                                                     |     |              |
                                                   --^-----^--------------^-- 0v

 

[munsta88]

thanks for the reply mate!


thought id take a shortcut and not bother soldering and measuring the currents.

heres what i found after removing the outer plastic coating around the 3.5mm jack.

http://img356.imageshack.us/my.php?image=dsc02644av4.jpg

It only seems to have 2 solder joints, so im not entirely sure what to do? which wire is tip? ring? sleeve? any help please?


THanks btw!

 

[Dippy]

If it only has 2 solderable connections and no visible sign of a third then put it in the drawer or bin.
Was it just a mono earpiece type thing? Not stereo headphones.

 

[munsta88]

it was from some old random earphones i found lying about. Question is, as hippy said shouldnt the GND go to the sleeve?

EDIT:: i found a small blob of solder on the sleeve which i think was the connection for the GND.

EDIT::::: oh **mn! just realised something. How do i know which of the two visible solder joints on the picture goes to tip/ring? any usual orders?

 

[Dippy]

Strangely enough, we haven't all got that connector lying around. A clue maybe in; how would you manufacture the connector? How would you arrange the conductors if you were making it?

HOW ABOUT TESTING IT!
Multimeter?
Battery, wires, light bulb?
Battery, wires, peeper?
Battery, wires, resitor, LED?

Anything to check continuity???
You must have something lying around surely.

But, if you want to take a shortcut then you may as well guess.

 

[hippy]

Ah ... you trimmed it right back to just the plug. I'd personally say forget it, buy a 3.5mm Jack with three solder pads or invest in a ready built download cable.

 

[moxhamj]

There is nothing wrong with recycling and it may be possible to get this working but you will need a multimeter. Connecting it up randomly is likely to result in -12V being applied to the data output line of the picaxe and that will zap it. Follow the circuit diagrams in the manual carefully. Then when you are absolutely sure you have it right, check it again with the voltmeter. If you are building on a breadboard, build everything but don't put the chip in yet. Then measure the volts where physical leg 2 will go and where physical leg 7 will go. If you have it wired up right and it is connected to the PC you will have a negative voltage on the leg 2 socket and no volts on the leg 7 socket. Then try doing a dowload. It will fail, but you will see the volts on the leg 2 socket go positive. Only then is it safe to put the chip in.

A multimeter will cost less than $10. A dowload cable is even cheaper.