Post by thread:[PIC]: Inductive sensor & Coins

Hello Javier & PIC.ers, > >Date: Thu, 5 Apr 2001 02:32:15 -0300 >From: Javier <.....mariosabino007KILLspam@spam@HOTMAIL.COM> >Subject: [PIC]: Inductive sensor & Coins >MIME-Version: 1.0 >Content-Type: text/plain; charset="iso-8859-1" >.Content-Transfer-Encoding: 8bit > >Hi >Do you know how ticket machines detect the values of the inserted coins ? >I4ve heard inductive sensors, is that right ? Can I build the sensor with 2 >coils ? .. I've had recent exposure to these. It looks like the coin is tested inductively for go/no-go. The clever bit is that the acceptor mechanism holds a reference coin, the exact same as the intended type. The characteristics have to match. I suppose a multiple-coin type has places for many reference coins. .. >I want to do this kind of project with a PIC any hints ? >Bye >Javier > Unrelatedly, but someone lately was looking for help with an air-flow sensor. The dandiest design I've seen uses a (ptc) thermistor in the flow (I *know*, I *know* those things are very non-linear...) Anyhows, this little matter was gotaround by configuring the part in a simple feedback cct. that maintained the ugly thermistor at a constant temperature.... >> ie constant PD. As flow changes, the current required to maintain the PD changes, and this is measurable & linear. Well, I suppose it is if you assume the heat transfer rate is proportional to flow rate, maybe only true in laminar conditions, or maybe only true in turbulence, or, ... what is this leading to... best regards, John e-mail from the desk of John Sanderson, JS Controls. Snailmail: PO Box 1887, Boksburg 1460, Rep. of South Africa. Tel/fax: Johannesburg 893 4154 Cellphone no: 082 741 6275 email: jsandKILLspampixie.co.za Manufacturer & purveyor of laboratory force testing apparatus, and related products and services. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

I fix coin acceptors all of the time. Coils are arranged to measure the thickness, diameter, and material (2 measurements) content of the coins inserted. A value is obtained for each parameter which is then compared to values stored in non-volatile memory. If the value is within the "windows" stored in the memory, the coin is accepted. A further piezo "knock" sensor is used to measure how hard the metal is. Currently 16 coins can be validated. If you only want to use two inductors, you will have major problems with accepting false coins. Regards BBB -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads