Post by thread:[PIC]: Input activated by TV?

Dear All I have a PIC(16F84) close to my TV and video recorder that monitors micro switches and record video when certain things happen. I have connected RA1 to +5V through a 1K resister to pull it logic high and RA1 through a microswitch to GND to pull it logic low when the microswitch closes. My problem: Every time when I switch the TV off the PIC acts if the microswitch was activated...but it is not. I have disconnect the TV from everything else exept the mains power and the problem still remain. Strangely enough is that all the other functions of the PIC seems to be normal. It don't seems like the PIC resets or anything because after a 20 second delay subroutine the PIC must stop the recording and it does so.... Thanks Kindest Regards Francois Robbertze lllllllllll \\ ~ ~ // ( @ @ ) o------oOOo-(_)-oOOo-----o | | | Francois Robbertze | | spam_OUTfr10TakeThisOuTmweb.co.za | | | o--------.oooO-Oooo.-------o -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use .....listservKILLspam@spam@mitvma.mit.edu?bodyT%20PICList%20DIGEST

Francois, Sound like you may have EMI problem. do this 1.unplug your TV and connect any light bulb or any thing that you can see then it is on or off see if the TV is causing it if yes then you PIC needs some changes. 2. remove the micro switch and connect RA1 to +5 v driect and turn your TV on/Off see if it happening again if yes that means your pic gets interrupted thru other I/O wire unused I/O to ground or in software make them output. if no then the problem is where your micro switch is try using shielded cable bla bla. we will talk more about it later as soon as I know more about it. If you have any wire going under the TV or close to the TV it will act like antenna and the PIC is sensitive enough to pic it up as a signal. let me know about it. Andre Abelian {Original Message removed}

> >Every time when I switch the TV off the PIC acts if the microswitch was >activated...but it is not. >I have disconnect the TV from everything else exept the mains power and >the problem still remain. Strangely enough is that all the other functions >of the PIC seems to be normal. It don't seems like the PIC resets or >anything because after a 20 second delay subroutine the PIC must stop the >recording and it does so.... I don't know the whole mechanism of it, but when you switch many CRTs off, the voltage at the face rises dramatically. I bet you are using relatively large resistance values. Try a low value pullup/down resistor on your switch line. -- Where's dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9 -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use listservKILLspammitvma.mit.edu?body=SET%20PICList%20DIGEST

Build a debouncing routine into the PIC code. Require ~100 msec of microswitch closed before starting the action (recording you said). Apply the same treatment to all switch and sense inputs actuated by humans (slow). Other inputs (faster) may require more effort. hope this helps, Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's

>I don't know the whole mechanism of it, but when you switch many CRTs off, >the voltage at the face rises dramatically. I bet you are using relatively >large resistance values. Try a low value pullup/down resistor on your >switch line. The voltage on a CRT face drops to obscene negative values when turned off (it raises when turned on). The reason is the capacitance coupling the screen mask (at ~35kV) inside to whatever is at the other side of the screen. The HV almost instantly collapses by at least 10kV at turn off. If you have anything CMOS coupled to the screen face (like a sense screen) then you will have problems. You will have problems even at 2 feet with open CMOS inputs, esp. unprotected ones. There was a certain make of TV on the market that constantly fried its own IR remote sensor like this until a replacement was devised. The replacement has a miniature grounded Faraday cage made of stamped metal around it ;-). Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's

No this is used most of the time on for example alarm contact's Regards Art ----- Original Message ----- From: Francois Robbertze <.....fr10KILLspam.....PIXIE.CO.ZA> To: <EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU> Sent: Saturday, September 30, 2000 10:12 PM Subject: Re: [PIC]: Input activated by TV? {Quote hidden}> I have connected a 104 cap over the microswitch... > > Is this bad practise? I dont know, but it seems to work quite well! > > Regards > > Francois > > ----- Original Message ----- > From: Peter L. Peres <plpspam_OUTACTCOM.CO.IL> > To: <@spam@PICLISTKILLspamMITVMA.MIT.EDU> > Sent: Friday, September 29, 2000 12:01 AM > Subject: [PIC]: Input activated by TV? > > > > Build a debouncing routine into the PIC code. Require ~100 msec of > > microswitch closed before starting the action (recording you said). Apply {Quote hidden}> > the same treatment to all switch and sense inputs actuated by humans > > (slow). Other inputs (faster) may require more effort. > > > > hope this helps, > > > > Peter > > > > -- > > http://www.piclist.com hint: PICList Posts must start with ONE topic: > > "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's > > > > > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

part 1 2427 bytes content-type:text/plain; (decoded 7bit) Dear Victor, Attached, please find a the connections to the switch - hope this make sence.. Please also read the message from Richard Prosser. He sugest to put a resister in series with the cap. Regards Francois Robbertze {Original Message removed} part 2 326 bytes content-type:text/plain; (decoded 7bit) ___ I I +---> +5V I I I I P I I / I I-+-----+-----+--*/ *--+---+>GND I I I I S1 I I I I I I C I +---II----+ I I 0.1uF Cap(104) I___I part 3 133 bytes -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use KILLspamlistservKILLspammitvma.mit.edu?body=SET%20PICList%20DIGEST

part 1 3157 bytes content-type:text/plain; (decoded 7bit) Hi: You must use a series resistor (pull up) to avoid a short when swith is close... look at new attached file... Regards, Gonzalo {Original Message removed} part 2 449 bytes content-type:text/plain; (decoded 7bit) I +---> +5V I > < ___ > R = 10K I I < I I I I P I I / I I-+-----+-----+--*/ *--+---+>GND I I I I S1 I I I I I I C I +---II----+ I I 0.1uF Cap(104) [COULD BE 103 ALSO] I___I part 3 133 bytes -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use RemoveMElistservTakeThisOuTmitvma.mit.edu?body=SET%20PICList%20DIGEST

part 1 4139 bytes content-type:text/plain; charset=iso-8859-1 (decoded quoted-printable) Thanks for the correction in my scematic... I have another problem with this configuration. Sometimes (or can I say most of the times) when I close a switch, the PIC resets. Why? (If I remove the cap over the switch the PIC don't reset when I close a switch) Francois Robbertze {Original Message removed} part 2 462 bytes content-type:text/plain; name=Cap.txt (decoded quoted-printable) I +---> +5V I > < ___ > R = 10K I I < I I I I P I I / I I-+-----+-----+--*/ *--+---+>GND I I I I S1 I I I I I I C I +---II----+ I I 0.1uF Cap(104) [COULD BE 103 ALSO] I___I part 3 105 bytes -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestspamBeGonemitvma.mit.edu

Try this. At swich on the logic state is unprdicable as you may still have voltage on the cap with the switch open. In the ideal world the start up state the cap is at 0volt this is charged up to a logic 1 when you close the switch the logic level is 0 agian. you will also need a diode anode to the positive supply rail so when unit is switched off the cap is discharged. Regards Art {Original Message removed}