Need help building leds for Model F keyboard

[berserkfan]

Being an ignorant peasant like the character Gutz, I have neither knowledge nor experience with building electrical circuits.

Being gutzy like him, I am willing to try.

I don’t quite get what I am supposed to do, so here is my ignorant picture. Someone please correct me before I fry my teensy!

What I need advice are:

1)   What type of resistor to use. I’m presuming the 3.3v but don’t really know the part number.

2)   How to hook up that resistor.

3)   Which leg of led to attach that resistor to, and what to do with the other led leg.

4)   How to mount leds properly to something. I prefer something more intelligent and attractive than my usual hot glue solution. Suggestions on ways to mount SIP sockets are welcome because I love using SIP sockets.

5)   Finding an LED overlay less boring than these http://pckeyboard.com/page/Misc/LED. I suspect I will end up making my own from my Brother P-touch printer, so this is not an important issue.

6)   How to properly dremel Model F cases to avoid creating a disastrous web of cracks.



Now throwing my question out to the geekcloud. The cloud of geeks' response is...

[suicidal_orange]

1) Resistors are rated as a max voltage - 3.3-5v on a Teensy is nothing, so get cheap ones.  Tolerance (%) isn't important but if you want them all identically bright lower % is a closer match, or get lots of higher % (cheaper) ones and test them yourself.  You need through hole not SMD

The main spec to worry about is the resistance - see here for an explanation of how to calculate the proper resistance if you know your LED specs, if you don't know start with 100ohm and reduce if too dim or raise if too bright. 

2) Typically PXX pin -> resistor -> [long leg] LED [short leg] -> ground pin

3) See 2.  One way it lights up the other it doesn't - no damage will be done if you get it wrong so just touch the legs to the wires to confirm before soldering.

4) I like hot glue, I'll leave aesthetics to someone else )

5) See 4!

6) I would suggest medium speed and low pressure when dealing with plastic to avoid melting, but have no experience with a Model F case or anything old and crackly.  What are you trying to do exactly? (cut, drill, )

[berserkfan]

1) To calculate the voltage on a teensy, the source from USB is 3.3v? I’m really quite clueless.
2) So you mean that for 3 lock lights, I will have 3 leads to the teensy ground pin (in addition to the lead already coming from the Model F keyboard? I’m kind of wondering how people manage to solder 4 wires to the same pad.
4) Do you have any advice on hot glue? I just buy the cheapo generics from a shop near my place, $1+ for 8 glue sticks. That’s cheap, but I just don’t know how long they will last.
6) I originally read your “crackly” as “cranky”, which isn’t far from the truth. Originally I was thinking of both cutting and drilling, but now I think I’ll just drill 3 holes.

As for the cutting, lemme explain. Last year WCass and Fohat came up with ways to recycle old M casings for the Model F. Most of the cutting can easily be done on plastic. Unfortunately, I missed Wcass’ last photo, where he points out we also need to cut the Model F plate. And it’s pretty thick metal. I don’t see myself doing a great job on that, so decided to stick with my broken casing.

[suicidal_orange]

1) USB is 5v, but you're using the IO pins so you need to find out the logic voltage for your controller (I'm sure this has a name but can't think of it) - a Teensy 2.0 or 3.1 is 5v, the Teensy 3.0 and some others are 3.3v.  You said 3.3v resistors so I went with that...  If 5v you'll want to start with a higher resistance if you're guessing your LEDs specs.

2) Yup, everything goes to ground eventually!  If you have space it's probably worth putting in an actual pin rather than trying to solder four wires to the pad, then you can loop all the wires round it before soldering them all at once a bit above the controller.  If you don't have the height for that you can solder one wire to the controller and solder the others on to that.

4) As far as I know hot glue is hot glue and it's pretty durable so unless you're planning to beat someone over the head with your keyboard or take it to the arctic I doubt it will be an issue.  Though maybe it's a bit hot for it where you live?  If in doubt you could use Sugru, that will hold pretty much anything (let me know if you'd like a pack, any colour as long as it's black ))

6) I guess this thick metal is steel?  Probably wise to leave it alone, I was cutting a 2mm thick steel case and that went through many carbon cutting disks even once I got the technique right and stopped shattering them.  If you do want to try it cut slightly small and then file larger, and don't forget your safety goggles!