Post by thread:[EE]: Mouse Encoder Circuit Question

Hi, I am trying to hack a mouse encoder to use as a shaft encoder for a mobile robot. I removed the slotted wheel, IR LED, and what I assume is a photo-transistor from a mouse. The Phototransistor is housed in black plastic and has three leads. I was wondering if anyone could give me a circuit so I can interface the (photo-transistor ?) to a PIC. I want to power the IR Led and then use the int on change function of portb to record the pulses from the photo-transistor. ( It mat not be a photo-transistor, but that's my best guess) I have spent several hours searching the net for a circuit on how to do this, but no luck. Any help would be appreciated. Thanks, Kevin -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

> I am trying to hack a mouse encoder to use as a shaft > encoder for a mobile robot. I removed the slotted wheel, > IR LED, and what I assume is a photo-transistor from a mouse. > The Phototransistor is housed in black plastic and > has three leads. I was wondering if anyone could give me > a circuit so I can interface the (photo-transistor ?) to > a PIC. I want to power the IR Led and then use the int on > change function of portb to record the pulses from the > photo-transistor. ( It mat not be a photo-transistor, > but that's my best guess) A phototransistor is like a regular bipolar transistor (usually NPN) except that it also turns on when light shines on it. The two important questions are how much current will it pass when light is shining on it in your application, and how much current will it leak when the light is being interrupted. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

Examine the mouse board to find the common pin then use 100k pull-ups (if common was GND) or pull-downs (if the common was +Vcc). Also route each output to a PIC input pin. Peter On Wed, 14 Aug 2002, Kevin A. Benedict wrote: {Quote hidden}>Hi, > >I am trying to hack a mouse encoder to use as a shaft >encoder for a mobile robot. I removed the slotted wheel, >IR LED, and what I assume is a photo-transistor from a mouse. >The Phototransistor is housed in black plastic and >has three leads. I was wondering if anyone could give me >a circuit so I can interface the (photo-transistor ?) to >a PIC. I want to power the IR Led and then use the int on >change function of portb to record the pulses from the >photo-transistor. ( It mat not be a photo-transistor, >but that's my best guess) > >I have spent several hours searching the net for a circuit >on how to do this, but no luck. >Any help would be appreciated. > >Thanks, >Kevin > >-- >http://www.piclist.com hint: To leave the PICList >piclist-unsubscribe-requestKILLspammitvma.mit.edu > > > -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Just a note: Kevin, please don't use a reply-to address with your piclist email. It caused my reply to go straight to you, and not to the list. Many people on the list do not appreciate telling only one person their answer. Now back to my original message. - --- I assume that the mouse has two of these encoders, no? If so, look at the voltages on the still functioning encoder, and try to hack the circuit out from there. Also, I've been pretty sure that mice usually operate on two IR LED/Phototransistor pairs. So, each wheel has two sets, and they produce a quadrature output when placed properly. That will take some adjusting to get it right. Once you have a quadrature output, you can either use a commercial quadrature decoder chip (eg. LS7084. Go to http://www.chipcenter.com/questlink to find datasheets), or write your own software to handle it. - - {Original Message removed}

Hi Everyone, Thanks for the input, I probably won't get to experiment with the encoder until next week unfortunately. :( Brendan, the mouse I have only has one encoder per wheel, but I will test out the circuit and see what I come up with. Also, I usually do delete my address in the reply to field. I must have forgot, at least I remember the topic tags !!! Thanks again, Kevin -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu

From David Duffy >The 3 pin IR detector may be 2 IR detectors with a common lead? >Does the encoder have 2 sections - one 2 pin and the other 3 pin? >I'd think that it'd have to otherwise it couldn't detect the direction. I got a nice Infrared Picture of the phototransistor, and three other pictures of the mouse circuit, about 200kb all together. www.members.dca.net/kben/misc/mouse.html Like they say, a picture is worth a thousand words. Any comments on interfacing the ir led and phototransistor to a PIC are welcome. Thanks, Kevin -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Kevin wrote: >Hi Everyone, >Thanks for the input, I probably won't get to >experiment with the encoder until next week >unfortunately. :( > >Brendan, the mouse I have only has one encoder >per wheel, but I will test out the circuit and >see what I come up with. The 3 pin IR detector may be 2 IR detectors with a common lead? Does the encoder have 2 sections - one 2 pin and the other 3 pin? I'd think that it'd have to otherwise it couldn't detect the direction. Regards... ___________________________________________ David Duffy Audio Visual Devices P/L U8, 9-11 Trade St, Cleveland 4163 Australia Ph: +61 7 38210362 Fax: +61 7 38210281 New Web: http://www.audiovisualdevices.com.au ___________________________________________ -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> >From David Duffy > >The 3 pin IR detector may be 2 IR detectors with a common lead? > >Does the encoder have 2 sections - one 2 pin and the other 3 pin? > >I'd think that it'd have to otherwise it couldn't detect the direction. Kevin wrote: >I got a nice Infrared Picture of the phototransistor, >and three other pictures of the mouse circuit, about >200kb all together. >www.members.dca.net/kben/misc/mouse.html >Like they say, a picture is worth a thousand words. It's too hard to see the transistor properly in the picture. I just opened up a cheap mouse here and it looks like each IR receiver is indeed a dual unit. One pin on each receiver goes to +5V and the other two pins on each go to the micro using 4 port pins in all for detection. The IR LEDs are wired in series with a 1K2 resistor & hung between 0V & +5V. Yours should be very similar. The Q1 & Q2 designations are a bit misleading. They're not photo-transistors in the "normal" sense of the 3 pin variety with a base connection. :-) I hope this helps. Regards... ___________________________________________ David Duffy Audio Visual Devices P/L U8, 9-11 Trade St, Cleveland 4163 Australia Ph: +61 7 38210362 Fax: +61 7 38210281 New Web: http://www.audiovisualdevices.com.au ___________________________________________ -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Kevin A. Benedict wrote: > > >From David Duffy > >The 3 pin IR detector may be 2 IR detectors with a common lead? > >Does the encoder have 2 sections - one 2 pin and the other 3 pin? > >I'd think that it'd have to otherwise it couldn't detect the direction. > > I got a nice Infrared Picture of the phototransistor, > and three other pictures of the mouse circuit, about > 200kb all together. > http://www.members.dca.net/kben/misc/mouse.html > Any comments on interfacing the ir led and phototransistor > to a PIC are welcome. Hi Kevin, that IR sensor is a dual IR photodiode. It has one common pin and two pins for the outputs of the 2 separate IR diodes. These are easy to interface to the PIC, you can run the LED with a few mA, normally about 5mA, and connect the IR diode(s) via a high value resistor to +5v. Try about 56k to start. The IR diode is REVERSED. When NOT illuminated the IR diodes have little leakage and will act open circuit, so the voltage to the PIC is a logic HI. When illuminated with IR, the diode resistance drops to a few k ohms, and the voltage to the PIC goes to a logic LO. Like this: a k 0v (gnd)------->|-------*----R1------- +5v IR diode | 56k | | output to PIC -Roman PS. Can you FIX your reply-to address!!!! -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Hi Roman, et all, You are in deed correct. I put the photodiode on a breadboard, and attached my DMM to it. I read 500K when no IR light was present. I shined the IR light from my digital camera on the photohdiode and the resistance dropped to practically nothing. Thanks ! P.S. I changed my reply to address to the piclist {Quote hidden}>Kevin A. Benedict wrote: >> >> >From David Duffy >> >The 3 pin IR detector may be 2 IR detectors with a common lead? >> >Does the encoder have 2 sections - one 2 pin and the other 3 pin? >> >I'd think that it'd have to otherwise it couldn't detect the direction. >> >> I got a nice Infrared Picture of the phototransistor, >> and three other pictures of the mouse circuit, about >> 200kb all together. >> http://www.members.dca.net/kben/misc/mouse.html > >> Any comments on interfacing the ir led and phototransistor >> to a PIC are welcome. > > >Hi Kevin, that IR sensor is a dual IR photodiode. >It has one common pin and two pins for the outputs >of the 2 separate IR diodes. > >These are easy to interface to the PIC, you can run >the LED with a few mA, normally about 5mA, and connect >the IR diode(s) via a high value resistor to +5v. >Try about 56k to start. The IR diode is REVERSED. > >When NOT illuminated the IR diodes have little leakage >and will act open circuit, so the voltage to the PIC >is a logic HI. > >When illuminated with IR, the diode resistance drops >to a few k ohms, and the voltage to the PIC goes to >a logic LO. > >Like this: > a k > 0v (gnd)------->|-------*----R1------- +5v > IR diode | 56k > | > | > output to PIC > >-Roman >PS. Can you FIX your reply-to address!!!! > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 > P.S. I changed my reply to address to the piclist If you simply remove your reply-to address entirely, it will do the same job. ;o) - --Brendan -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 6.5.8 for non-commercial use <http://www.pgp.com> iQA/AwUBPVvWCgVk8xtQuK+BEQJAJQCg4jzilvM1hGCUM497ZhJrzjxRnYgAoK1c /ESoNIctMAnFbAYIA4eX8W8g =kbjm -----END PGP SIGNATURE----- -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads