Post by thread:optical rotary encoders with PICs

Dear All, This is my first post and I am very impressed at the level of knowledge. And since I have none, I am up for a lot of reading. Anyway, this is a bit of a general electronics question. I want to make a rotary switch for a HiFi preamplifier project. It is used to select the source and volume on pre-amplifier and the signal from the switch goes to the PIC. (with maybe some electronics in between). The switch needs to be able to distinguish clock or anti-clockwise. And little else. The end effect is similar to many PPL commercial radios with tuning knobs that free wheel. I believe that there is such a thing as an optical rotary encoder that will give me a required signal. I recently opened a dead mouse and it has the exact parts I want, but obviously I can't use it. If there is such a thing as an simple optical rotary encoder that can be mounted on a front panel of an Amplifier project. Tell me where to get it... Anson PS. I live in the UK, so only UK retailers please!

>If there is such a thing as an simple optical rotary encoder that can be >mounted on a front panel of an Amplifier project. Tell me where to get it... > >Anson > >PS. I live in the UK, so only UK retailers please! Hi, If you find them at a reasonable price (RS charges 45 quid - ouch) could you let me know too. If a mouse can be sold for five quid with two of them in it there must be someone making them cheaply. Thanks, Keith. P.S. If you want to get one from RS mail me and I'll send you the part no. ========================================================== Keith Dowsett "Variables won't; constants aren't." E-mail: spam_OUTkdowsettTakeThisOuTrpms.ac.uk WWW: http://kd.rpms.ac.uk/index.html

Anson Chuang <.....anson.chuangKILLspam@spam@dial.pipex.com> writes: > > I recently opened a dead mouse and it has the exact parts I want, but > obviously I can't use it. > > If there is such a thing as an simple optical rotary encoder that can be > mounted on a front panel of an Amplifier project. Tell me where to get it... > I had the same problem a few weeks ago. I found a few sources for such parts, but they all were too expensive for my application. I couldn't get any optical encoders below $40. If cost is not an issue to you, you can get optical encoders by HP or Bourns, e.g. Look up UK suppliers at their homepage, I can't help you there since I live in germany. (If memory serves me well, I found some HP parts in the Farnell catalogue, which you should have in the UK, too) For my project I finally bought mechanical encoders, since I didn't need the higher resolution of the optical parts. I got Bourns mechanical encoders with 32 steps per rotation. These have mecanical clicks, which is not ideal for my application, but I got them for 7DM ($5) at Farnell's so what the heck... I hope that helps you... PS: If you find cheap optical encoders, pleas mail me, I am still interested! Bye Aki

At 18:08 07/01/97 +0100, Aschwin Gopalan wrote: >Anson Chuang <anson.chuangKILLspamdial.pipex.com> writes: > >> >> >> If there is such a thing as an simple optical rotary encoder that can be >> mounted on a front panel of an Amplifier project. Tell me where to get it... >> > >For my project I finally bought mechanical encoders, since I didn't need the >higher resolution of the optical parts. I got Bourns mechanical encoders with >32 steps per rotation. These have mecanical clicks, which is not ideal for >my application, but I got them for 7DM ($5) at Farnell's so what the heck... > Do mechanical encoder provide the CW, CCW triggers that I am looking for? I don't have that many data lines left on my '84. Only PA4, and PortB bus left... Anson

In message <.....2.2.32.19970107115700.006863e8KILLspam.....pop.dial.pipex.com>, Anson Chuang <EraseMEanson.chuangspam_OUTTakeThisOuTDIAL.PIPEX.COM> writes {Quote hidden}>Dear All, > >This is my first post and I am very impressed at the level of knowledge. And >since I have none, I am up for a lot of reading. > >Anyway, this is a bit of a general electronics question. I want to make a >rotary switch for a HiFi preamplifier project. It is used to select the >source and volume on pre-amplifier and the signal from the switch goes to >the PIC. (with maybe some electronics in between). > >The switch needs to be able to distinguish clock or anti-clockwise. And >little else. The end effect is similar to many PPL commercial radios with >tuning knobs that free wheel. I believe that there is such a thing as an >optical rotary encoder that will give me a required signal. > >I recently opened a dead mouse and it has the exact parts I want, but >obviously I can't use it. > >If there is such a thing as an simple optical rotary encoder that can be >mounted on a front panel of an Amplifier project. Tell me where to get it... > >Anson > >PS. I live in the UK, so only UK retailers please! Cirkit have an inexpensive mechanical encoder in their catalogue. It looks a bit like a rotary switch, and is much cheaper than the optical ones, but won't last as long. We make our own optical encoders where I work, for our military radios. It's basically a disk with slots cut in it. The "fingers" are then bent over at right angles to produce a sort of slotted cylinder - very cheap, and it's easy to mount the IR LED emitters and IR sensors. Leon -- Leon Heller, G1HSM leonspam_OUTlfheller.demon.co.uk Tel: +44 (0) 118 947 1424 (home) +44 (0) 1344 385556 (work)

In message <@spam@2.2.32.19970107115700.006863e8KILLspampop.dial.pipex.com>> KILLspamPICLISTKILLspamMITVMA.MIT.EDU writes: > If there is such a thing as an simple optical rotary encoder that can be > mounted on a front panel of an Amplifier project. Tell me where to get it... There's no need to use an expensive optical encoder, I believe the cheaper ones use conductive plastic, and would be quite suitable for a volume control. Many current 'mid-cost' audio units use encoders, as do some of the Pace satellite receivers (MSS500/1000), you could always try and obtain one as a spare part - if I remember, I'll try and find a price tomorrow. Nigel. /--------------------------------------------------------------\ | Nigel Goodwin | Internet : RemoveMEnigelgTakeThisOuTlpilsley.demon.co.uk | | Lower Pilsley | Web Page : http://www.lpilsley.demon.co.uk | | Chesterfield | | | England | | \--------------------------------------------------------------/

>Cirkit have an inexpensive mechanical encoder in their catalogue. It >looks a bit like a rotary switch, and is much cheaper than the optical >ones, but won't last as long. We make our own optical encoders where I >work, for our military radios. It's basically a disk with slots cut in >it. The "fingers" are then bent over at right angles to produce a sort >of slotted cylinder - very cheap, and it's easy to mount the IR LED >emitters and IR sensors. I have one of the older microsoft mice - the type that used a PC-card to use an LPT(2) interrupt so it looked like a PS/2 type. The Mouse is mechanical - has two code wheels X and Y and each code wheel has 2 sliding contacts (and still some lubrication even after 6 years). So you can generate pulse and direction by using a simple flip-flop, though use a schmitt with delay at the front end to remove extraneous pulses. I've seen this mouse sold around secondhand shops for about 5$. Mine still works after 6 years ! Even without extra vaseline and I use it every day. Rgds mike Socrates once gave the advice to "by all means get married... If you get a good wife you will become happy, if you get a bad one you will become a philosopher." Become an Engineer and avoid making this problematic decision.

> Anyway, this is a bit of a general electronics question. I want to make a > rotary switch for a HiFi preamplifier project. It is used to select the > source and volume on pre-amplifier and the signal from the switch goes to > the PIC. (with maybe some electronics in between). > > The switch needs to be able to distinguish clock or anti-clockwise. And > little else. The end effect is similar to many PPL commercial radios with > tuning knobs that free wheel. I believe that there is such a thing as an > optical rotary encoder that will give me a required signal. Why not use a simple DC motor? Bias at 2.5 V and feed into PIC A/D via an opamp + filter. The DC motor will give output with magnitude proportional to rpm and polarity of the direction of rotation. If you don't want the magnitude it might do with a pair of comparators. -- Martin

Anson Chuang <spamBeGoneanson.chuangspamBeGonedial.pipex.com> writes: > > Do mechanical encoder provide the CW, CCW triggers that I am looking for? I > don't have that many data lines left on my '84. Only PA4, and PortB bus left... > > Anson > Yes, they give you the same quadrature signals as the optical ones, that is two sqare wave signals. Depending on which edge comes first, you get the direction. You need two input pins on the PIC, one for each channel. You have to debounce them in software though. Its not really a problem, it took me about 30min, but thats just because am am a little dumb sometimes :-( I can lookup my code at home and mail it to you, though I think it is not quite an example of nice coding style... To clarify the operation of these things, let me show you a little ascii-art: Channel A ++-------++ ++-------++ ++-------++ || || || || || || || || || || || || || || || || || || ----------++ ++------++ ++------++ ++------- Channel B ++-------++ ++-------++ ++-------++ || || || || || || || || || || || || || || || || || || -----++ ++------++ ++-------++ ++------- This is for clock-wise rotation for example. As you can see, if you trigger on the rising edge of A, B is always high. For CCW rotation, at the rising edge of A, B is always low. So you can use one of the channels as a trigger and the other as direction output. All what is left is the debouncing. Another thing: look carefully at the manufactures specs on rotational lifetime of the part. The cheaper ALPS parts I found only had a lifetime of 10.000 rotations, which is not really much. The Bourns parts I am using now will last for 200.000 rotations, which is much better but still well below the 2 millions you can get out of optical encoders :-( Bye, Aki

> > Anyway, this is a bit of a general electronics question. I want to make a > > rotary switch for a HiFi preamplifier project. It is used to select the > > source and volume on pre-amplifier and the signal from the switch goes to > > the PIC. (with maybe some electronics in between). > > > > The switch needs to be able to distinguish clock or anti-clockwise. And > > little else. The end effect is similar to many PPL commercial radios with > > tuning knobs that free wheel. I believe that there is such a thing as an > > optical rotary encoder that will give me a required signal. > > Why not use a simple DC motor? Bias at 2.5 V and feed into PIC A/D via an > opamp + filter. The DC motor will give output with magnitude proportional > to rpm and polarity of the direction of rotation. If you don't want the > magnitude it might do with a pair of comparators. > > -- Martin > Ive used a stepper motor like this. Use two comparitors to clean up the signals from two of the phases and feed this into the PIC and use them like an ordinary encoder. Paul Waterfield Exhibit designer Techniquest Cardiff.

At 08:52 08/01/97 +0100, Martin Nilsson wrote: >> >> The switch needs to be able to distinguish clock or anti-clockwise. And >> little else. The end effect is similar to many PPL commercial radios with >> tuning knobs that free wheel. I believe that there is such a thing as an >> optical rotary encoder that will give me a required signal. > >Why not use a simple DC motor? Bias at 2.5 V and feed into PIC A/D via an >opamp + filter. The DC motor will give output with magnitude proportional >to rpm and polarity of the direction of rotation. If you don't want the >magnitude it might do with a pair of comparators. > > -- Martin > Good idea, but since the motor is next to some delicate audio equipment, I am unsure as to its noise contributions. Also, I only have equipment to program the '84s Anson

In message <RemoveME2.2.32.19970107115700.006863e8TakeThisOuTpop.dial.pipex.com>> PICLISTEraseME.....MITVMA.MIT.EDU writes: > If there is such a thing as an simple optical rotary encoder that can be > mounted on a front panel of an Amplifier project. Tell me where to get it... I checked on the encoder used on the Pace MSS500/1000 satellite receiver, it's a quadrature encoder (but not optical), and only costs 1.84 UK pounds + vat as a spare part from Pace. The manual gives the encoder the reference ECWOJ-C24-BE0024(200K-CYC), and the partnumber 146-0002420. On the circuit diagram it has three connections, 5 volts, anti-clockwise, and clockwise. Nigel. /--------------------------------------------------------------\ | Nigel Goodwin | Internet : EraseMEnigelglpilsley.demon.co.uk | | Lower Pilsley | Web Page : http://www.lpilsley.demon.co.uk | | Chesterfield | | | England | | \--------------------------------------------------------------/

Way back in January, in message <RemoveMEubenfwmpp9.fsfEraseMEEraseMEhelium.physik.uni-kl.de> Aschwin Gopalan <RemoveMEgopalanspam_OUTKILLspamPHYSIK.UNI-KL.DE> wrote: {Quote hidden}> Channel A > ++-------++ ++-------++ ++-------++ > || || || || || || > || || || || || || > || || || || || || > ----------++ ++------++ ++------++ ++------- > > > Channel B > ++-------++ ++-------++ ++-------++ > || || || || || || > || || || || || || > || || || || || || > -----++ ++------++ ++-------++ ++------- > > This is for clock-wise rotation for example. > > As you can see, if you trigger on the rising edge of A, B is always > high. For CCW rotation, at the rising edge of A, B is always low. So > you can use one of the channels as a trigger and the other as > direction output. All what is left is the debouncing. Looking at edges in this way is asking for trouble, hence you have to write things like debouncing routines etc. Really you should always look at examining the levels. A nice (fast!) compromise is documented in one of the Parallax data sheets, which is: Is the Current reading different from the previous? If so: Take the previous reading shift it to the right xor it with the current reading. Check bit 0 (or 2, 4, 6 etc...) If it is 0, then decrease the counter, else increase it. This works wonderfully. Consider the first two transitions in Aschwin's example (assume that count starts at 5, and the switch bounces a lot!) A: LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLHLLLLHHHHLLHHHHHHHHH B: LLLLLLLLLLHLLLLHHHLLHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH Change: NNNNNNNNNNYYNNNYNNYNYNNNNNNNNNNNNNNNNNNNNNNNYYNNNYNNNYNYNNNNNNNN Count: 5555555555655556665566666666666666666666666676666777766777777777 There's absolutely no way that the bounce can induce slippage, which it would with an edge-detecting algorithm. Using such a mechanism I've been keeping a serial-controlled resistor up to date and reading encoders at up to 12,000 pulses/sec on a 4MHz '84! (that's assuming one channel out of the 4 it's monitoring is changing, and guarantees that any pulse is seen) Fun! Stuart. -- Stuart Tyrrell Developments RemoveMEStuartTakeThisOuTspamstdevel.demon.co.uk PO Box 183, OLDHAM. OL2 8FB EraseMEstdevelspamspamBeGonelocust.co.uk (Mobile <> Email) Orange: 0976 255 256 (9am-9pm) http://www.stdevel.demon.co.uk *Analogue joystick i/face 39.95* *Using an IR keyboard via PS2Mouse 24.95*

Hi Guys, US Digital makes a nice chip that decodes the quadature inputs into a direction and clock pulse that could be easily interfaced to a PIC's interupt. On interupt, sample the direction and increment your counter. It also has some built in filtering. I only looked at quickly but it looked interested and was pretty cheap, ~2.00 US. I can dig out their contact info if your interested. Ben Wirz Electronics http://www.wirz.com At 10:18 AM 12/3/97 +0000, you wrote: {Quote hidden}>Way back in January, in message ><RemoveMEubenfwmpp9.fsfKILLspamhelium.physik.uni-kl.de> Aschwin Gopalan ><gopalanSTOPspamspam_OUTPHYSIK.UNI-KL.DE> wrote: > >> Channel A >> ++-------++ ++-------++ ++-------++ >> || || || || || || >> || || || || || || >> || || || || || || >> ----------++ ++------++ ++------++ ++------- >> >> >> Channel B >> ++-------++ ++-------++ ++-------++ >> || || || || || || >> || || || || || || >> || || || || || || >> -----++ ++------++ ++-------++ ++------- >> >> This is for clock-wise rotation for example. >> >> As you can see, if you trigger on the rising edge of A, B is always >> high. For CCW rotation, at the rising edge of A, B is always low. So >> you can use one of the channels as a trigger and the other as >> direction output. All what is left is the debouncing. > >Looking at edges in this way is asking for trouble, hence you have to >write things like debouncing routines etc. Really you should always look >at examining the levels. > >A nice (fast!) compromise is documented in one of the Parallax data >sheets, which is: > >Is the Current reading different from the previous? >If so: > Take the previous reading > shift it to the right > xor it with the current reading. > Check bit 0 (or 2, 4, 6 etc...) > If it is 0, then decrease the counter, else increase it. > >This works wonderfully. Consider the first two transitions in Aschwin's >example (assume that count starts at 5, and the switch bounces a lot!) > > A: LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLHLLLLHHHHLLHHHHHHHHH > > B: LLLLLLLLLLHLLLLHHHLLHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH > >Change: NNNNNNNNNNYYNNNYNNYNYNNNNNNNNNNNNNNNNNNNNNNNYYNNNYNNNYNYNNNNNNNN > >Count: 5555555555655556665566666666666666666666666676666777766777777777 > >There's absolutely no way that the bounce can induce slippage, which it >would with an edge-detecting algorithm. > >Using such a mechanism I've been keeping a serial-controlled resistor >up to date and reading encoders at up to 12,000 pulses/sec on a 4MHz >'84! (that's assuming one channel out of the 4 it's monitoring is >changing, and guarantees that any pulse is seen) > >Fun! > > > > >Stuart. >-- >Stuart Tyrrell Developments spamBeGoneStuartSTOPspamEraseMEstdevel.demon.co.uk >PO Box 183, OLDHAM. OL2 8FB KILLspamstdevelspamBeGonelocust.co.uk (Mobile <> Email) >Orange: 0976 255 256 (9am-9pm) http://www.stdevel.demon.co.uk >*Analogue joystick i/face 39.95* *Using an IR keyboard via PS2Mouse 24.95* >