Optical encoders from an old mouse - UK Vintage Radio Repair and Restoration Discussion Forum

Biggles · 15th Dec 2009, 10:27 pm

As I dismantled a discarded computer mouse the other day it crossed my mind that the optical position encoders could be used in home brew equipment for rotary tuning encoders and the like. As mice are "throw away" items nowadays they are in plentiful suppy. I haven't got round to scoping the output, and therefore do not know the format of the encoder pulses as they enter the computer, but it would be interesting to know if anyone has used them before.

Biggles.

dr peppers · 16th Dec 2009, 5:15 am

Never used a mouse encoder before but I have salvaged panel mounted rotary encoders of other equipment (videos etc) which are a similar thing, I've used them for menu selection on micro controller based projects mainly.

Panel encoders and mouse encoders are usually 'quadrature' encoders, there are 2 digital outputs (8 or 16 are popular for the pc mouse) on each encoder, you get 8 or 16 pulses per rev (depending on the resolution), the 2 digital outputs represent 2 phases, if phase a leads (comes before) b then the encoder is rotating one way, and if phase b leads phase a the encoder is going the other way, the frequency of the output is the speed the mouse is moving.

I come accross machine encoders at work also on a regular basis, and they work on exactly the same principle, with the exception that machine encoders also have a 'z' pulse, which is just a single pulse per rev that the machine uses at first switch on or reset.

New type pc mice dont use encoders any more, the current trend is an optical mouse, which is a basic video camera, the mouse has image processing software and calculates the movement and converts this to pulses, I know its odd having that much technology in a mouse, but peripherals are big business.

dominicbeesley · 16th Dec 2009, 1:39 pm

Hello,

Yes, as dr_peppers says above in old fashioned mouses there are a pair of opto-forks and a spoked wheel monitoring the pulse from each fork and comparing the relative phase gives speed, direction etc.

To make a rotary encoder involves getting the wheel to sit at the right position in the fork - this can be crtical and a bit fiddly but once its set it works fine. I've done this in the past by using the top of the spoked wheel as a sort of thumb wheel and also by gluing a flexible rod to the end of the shaft and taking that to the actual front panel wheel then I could just cut the mouse up to get one of the whole units and not have to bother about making a frame to hold them.

I'm about to make a DDS sig-gen / and intend to go the thumbwheel route for the fine tune and a reduction gear for the bigger main control knob...trouble is my construction skills are pretty rubbish so it probably will all fall to bits after an hour...it might be easier to just use the mouse as-is!

Dom

Biggles · 16th Dec 2009, 9:27 pm

Cheers. I'm not alone in trying to reuse junk for projects then. I would like to know more about your DDS project Dom, as I'm thinking of using a DDS chip as a local oscillator in an HF rig that I started building a (few years back!!) and technology has kindly overtaken me with the VFO so it would be handy to know which ICs to use although I accept that it will probably have to include a PIC of some kind as a controller. I have a PIC programmer/developer so I may be able to cope with that.

Biggles.

dominicbeesley · 17th Dec 2009, 6:16 pm

You're certainly not alone in being a junk lover! Whether its new or old I love to get something useful from "rubbish"!

I've ordered a DDS-60 "daughter board" from the States - no doubt will post something up here when I get round to putting it together - I aim to add a PIC, LCD read out, a couple of wheels for tuning and possibly a keypad and memories for Frequency selections. Just got back from a very frustrating abortive attempt at going to Farnell for the parts - gave up when with half a centimetre of snow on the ground the three tailgating idiots in front slid into each other! So will have to wait until after christmas to get the parts now!

I may order a "proper" encoder for the main tuner but will probably use the mouse bits for a fine tune thumbwhell.

Dom

dominicbeesley · 3rd Jan 2010, 3:43 am

Well I've jury rigged something up.

The DDS-60 kit came through a while ago today I plucked up the energy to go into the workshop. After an hour of soldering the minutest SMD components I've ever had to deal with it worked first time! Not easy with my shaky hands (too much Xmas/new year cheer I think). If you're thinking of getting one I'd say to pay the extra to get it made up unless you've got good eyesight I'm more or less 20/20 but was struggling at times!

Also, back on topic, I've hacked an old MS mouse for the rotary encoder and am now just trying to program it to work nicely - its not easy getting a single rotary control to tune nicely from 0-60MHz in 0.04Hz steps without either lots of twiddling or poor accuracy but I'm getting there. I think I'll end up with some buttons as well to choose fast/slow/medium ranges as well as an acceleration function on the tuning knob (i.e. when you turn it 2x as fast the number change 4/6/8 times faster etc).

Next up will be to rig this all up to a proper front-panel control...

Dom

PS: Sorry the photos are a bit rubbish had to use the phone

MODS: Is this sort of sig-gen too modern for the forum? I'm hoping to add a "wobbulator" mode to allow me to use it for aligning IF strips in radios / tellys so it is kind of on topic!

15th Dec 2009, 10:27 pm	#1
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Optical encoders from an old mouse As I dismantled a discarded computer mouse the other day it crossed my mind that the optical position encoders could be used in home brew equipment for rotary tuning encoders and the like. As mice are "throw away" items nowadays they are in plentiful suppy. I haven't got round to scoping the output, and therefore do not know the format of the encoder pulses as they enter the computer, but it would be interesting to know if anyone has used them before. Biggles.

16th Dec 2009, 5:15 am	#2
dr peppers Retired Dormant Member Join Date: Nov 2009 Location: Lancashire, UK. Posts: 67	Re: Optical encoders from an old mouse Never used a mouse encoder before but I have salvaged panel mounted rotary encoders of other equipment (videos etc) which are a similar thing, I've used them for menu selection on micro controller based projects mainly. Panel encoders and mouse encoders are usually 'quadrature' encoders, there are 2 digital outputs (8 or 16 are popular for the pc mouse) on each encoder, you get 8 or 16 pulses per rev (depending on the resolution), the 2 digital outputs represent 2 phases, if phase a leads (comes before) b then the encoder is rotating one way, and if phase b leads phase a the encoder is going the other way, the frequency of the output is the speed the mouse is moving. I come accross machine encoders at work also on a regular basis, and they work on exactly the same principle, with the exception that machine encoders also have a 'z' pulse, which is just a single pulse per rev that the machine uses at first switch on or reset. New type pc mice dont use encoders any more, the current trend is an optical mouse, which is a basic video camera, the mouse has image processing software and calculates the movement and converts this to pulses, I know its odd having that much technology in a mouse, but peripherals are big business.

16th Dec 2009, 1:39 pm	#3
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Re: Optical encoders from an old mouse Hello, Yes, as dr_peppers says above in old fashioned mouses there are a pair of opto-forks and a spoked wheel monitoring the pulse from each fork and comparing the relative phase gives speed, direction etc. To make a rotary encoder involves getting the wheel to sit at the right position in the fork - this can be crtical and a bit fiddly but once its set it works fine. I've done this in the past by using the top of the spoked wheel as a sort of thumb wheel and also by gluing a flexible rod to the end of the shaft and taking that to the actual front panel wheel then I could just cut the mouse up to get one of the whole units and not have to bother about making a frame to hold them. I'm about to make a DDS sig-gen / and intend to go the thumbwheel route for the fine tune and a reduction gear for the bigger main control knob...trouble is my construction skills are pretty rubbish so it probably will all fall to bits after an hour...it might be easier to just use the mouse as-is! Dom

16th Dec 2009, 9:27 pm	#4
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: Optical encoders from an old mouse Cheers. I'm not alone in trying to reuse junk for projects then. I would like to know more about your DDS project Dom, as I'm thinking of using a DDS chip as a local oscillator in an HF rig that I started building a (few years back!!) and technology has kindly overtaken me with the VFO so it would be handy to know which ICs to use although I accept that it will probably have to include a PIC of some kind as a controller. I have a PIC programmer/developer so I may be able to cope with that. Biggles.

17th Dec 2009, 6:16 pm	#5
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Re: Optical encoders from an old mouse You're certainly not alone in being a junk lover! Whether its new or old I love to get something useful from "rubbish"! I've ordered a DDS-60 "daughter board" from the States - no doubt will post something up here when I get round to putting it together - I aim to add a PIC, LCD read out, a couple of wheels for tuning and possibly a keypad and memories for Frequency selections. Just got back from a very frustrating abortive attempt at going to Farnell for the parts - gave up when with half a centimetre of snow on the ground the three tailgating idiots in front slid into each other! So will have to wait until after christmas to get the parts now! I may order a "proper" encoder for the main tuner but will probably use the mouse bits for a fine tune thumbwhell. Dom

3rd Jan 2010, 3:43 am	#6
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Re: Optical encoders from an old mouse Well I've jury rigged something up. The DDS-60 kit came through a while ago today I plucked up the energy to go into the workshop. After an hour of soldering the minutest SMD components I've ever had to deal with it worked first time! Not easy with my shaky hands (too much Xmas/new year cheer I think). If you're thinking of getting one I'd say to pay the extra to get it made up unless you've got good eyesight I'm more or less 20/20 but was struggling at times! Also, back on topic, I've hacked an old MS mouse for the rotary encoder and am now just trying to program it to work nicely - its not easy getting a single rotary control to tune nicely from 0-60MHz in 0.04Hz steps without either lots of twiddling or poor accuracy but I'm getting there. I think I'll end up with some buttons as well to choose fast/slow/medium ranges as well as an acceleration function on the tuning knob (i.e. when you turn it 2x as fast the number change 4/6/8 times faster etc). Next up will be to rig this all up to a proper front-panel control... Dom PS: Sorry the photos are a bit rubbish had to use the phone MODS: Is this sort of sig-gen too modern for the forum? I'm hoping to add a "wobbulator" mode to allow me to use it for aligning IF strips in radios / tellys so it is kind of on topic! Attached Thumbnails