rotary knob to keyboard encoder

yonu · 01-30-2007, 08:00 PM

does anyone here know of a DIY rotary to keyboard encoder plan I have a complete factory panel converted and wired to a keyboard encoder however I want to add a rotary knob to the panel as there is a space it will fit. but can't seem to find a converter priced below $40. So like I said does anyone know of plans for a DIY rotary to keyboard encoder?

Thanks,
Yonu

2k1Toaster · 01-30-2007, 08:14 PM

get a BCD rotary endoder and use a comparator to determine which direction it is going. Then use a if this direction then send code xxxx, if othe rdirection send yyyy, else not moving so no code.

yonu · 01-30-2007, 08:23 PM

any chance of diagram or a slightly more detailed description the coding makes sense and I looked up a encoder that is a BCD encoder bit I am having a little trouble picturing this setup

Thanks,
Yonu

yonu · 01-30-2007, 08:31 PM

I forgot to add that I have a rotary knob that I would prefer ro use as it is a double rotary on one shaft but if i can't use it oh well

Thanks,
yonu

2k1Toaster · 01-30-2007, 08:39 PM

well what I see is you want something where you turn the knob to the left, it sends a 'L' key to the computer. If you turn it right, then it sends 'R' or something. That way you can control it.

So if you get a BCD knob it will send out a binary value depending on where it is.

Have some clock at a relatively slow speed like 10Hz or maybe 15Hz where it saves the current value to a memory block, and then use a 3 value comparitor to compare the BCD in memory to the one currently on the knob. If the current position is greater than the previous value, then it is being turned clockwise. If the value is less, then counterclockwise. If no change, then not moving.

This is all hardware end.

Now use the left/right/no_movement output of the comparator to a keyboard circuit to send whatever key you want on each of those values.

yonu · 01-30-2007, 09:00 PM

ok 2 questions what kind of price would I be looking for on the BCD knobs as i havn't had much luck finding one that has a price on it just information about them

Thanks,
Yonu

2k1Toaster · 01-30-2007, 09:11 PM

I find them at local electronics junk stores. Usually about $1 to $3 for a cheap one.

yonu · 01-30-2007, 09:16 PM

all we have around here is radio shack and a little wannabe electronic store would it be labeled as BCD? and I take it the the comparator would be labeled comparator? sorry I am used to repairing and hacking existing items not scratch building

Thanks,
Yonu

2k1Toaster · 01-30-2007, 09:37 PM

Here are really cheap parts from the early 80's if not before. Meaning really cheap. THey still work.

Nowadays they use PIC's. After TTL, there was CMOS, and now there are fully programmable chips.

74LS page: http://www.unicornelectronics.com/IC/74LS.html

74LS682 (An 8bit comparator): http://www.unicornelectronics.com/ft...84-685-688.pdf

Truth table is on page 2 of the pdf.

2k1Toaster · 01-30-2007, 09:38 PM

One of the comparator chips is $1.50 just to let you know.

LS just means a a low power version.

TTL runs off of 5v, and CMOS uses 3.3v.

2k1Toaster · 01-30-2007, 09:43 PM

Quote: Originally Posted by yonu

all we have around here is radio shack and a little wannabe electronic store would it be labeled as BCD? and I take it the the comparator would be labeled comparator? sorry I am used to repairing and hacking existing items not scratch building

Thanks,
Yonu

BCD: Binary Coded Decimal. Instead of giving you this:

0: 1000
1: 0100
2: 0010
3: 0001

it gives you this:

0: 00
1: 01
2: 10
3: 11

yonu · 01-30-2007, 09:57 PM

Thanks I will look into that.
Question can you get dententless(sp?) encoders in this type?

Thanks,
Yonu

MrJamieR · 01-31-2007, 02:05 AM

Would an Audi style MMI style rotary encoder do the trick?
TonyG has a great thread on his solution. (Actually it's better than great it's gobsmacking.)
http://www.mp3car.com/vbulletin/show...&highlight=mmi

yonu · 02-01-2007, 07:02 AM

I looked in to Tonyg's and unless I am mistaken his uses a mouse board I would prefer to tie it into my keyboard encoder as that alone is a tight fit and I already have about 5 buttons on it now and about 2 more to add so I would prefer not to change it. I also attempted to hack a mouse just for the encoder but have had no luck with getting it to work so I think first of the week I am going to order the parts to build one. Thank you for the info though

Thanks,
Yonu

yonu · 02-04-2007, 07:44 PM

well I ended up dropping the rotary encoder from the panel as I was unable to find a encoder that would fit with the clerance I have behind the panel. Thanks for the help on it

On a similarly related topic what would be required to split off say 3 switches that use a single resistance wire into 3 wires( resistors or a full blown circuit?

Thanks,
Yonu