12-volt matrix input->output?
in [Design]
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From: John E. on 25 Feb 2007 05:05 Thus spake Jan Panteltje: > If you connect the thing as above, you save 4 diodes by connecting all > resistors > that hold the gates down to output 7 of the CD4051, so if output 7 goes high, > then all MOSFETS are powered, and all lights go on. > You need these resistors anyways. Sort of using 4015 output pin 7 as a pull-down resistor for the MOSFET's gates? What MOSFET would you recommend? I might want to power 2 relays in parallel with each of the 4 MOSFETs... Is this 60v N-channel one, with 1.2 ohm on-resistance an appropriate choice? : <http://www.jameco.com/Jameco/Products/ProdDS/256031FSC.pdf> And it includes a diode (which will act as a flyback, yes?) And about input conditioning: mechanical switch contacts will be "not clean", probably causing problems with bouncing, noise, etc. Best way to clean up these inputs? Thanks, -- John English
From: John E. on 25 Feb 2007 05:09 > it's going to take three chips .... > Jasen Jasen, I really appreciate the fresh approach of looking at the inputs as logical inputs and using a Boolean solution, but I think I'll stick with the 1-chip solution (and a few diodes and resistors and MOSFETs). I've seen several of your creative suggestions in these groups. Maybe I'll be able to utilize one next time... Thanks, -- John English
From: John E. on 25 Feb 2007 06:01 Jan Panteltje diagrams: > +12V > | > |---------- > k | > diode [ \ ] relay coil > a | > |---------- > | > |---- > A' -----| | Power MOSFET > | |---- > resistor | > 100k /// > | > | <- connect to output 7 of the CD4051 Just to clarify... The 2, 3, 4, 5, and 6 outputs connect to the 4 MOSFET gates via diodes. The 7 output connects to each of the MOSFET gates via resistors (instead of diodes). The resistors serve dual purpose of isolating (the term "open-collector" comes to mind) the gates from the outputs, and act as pull-down resistors also. Thanks, -- John English
From: John E. on 25 Feb 2007 06:05 Thus spake Bob n.: > But you didn't say the switches had to be single- > pole. The existing 3 input switches are simple on-off SPST. -- John English
From: Graham Holloway on 25 Feb 2007 06:10
"John E." <incognito(a)yahoo.com> wrote in message news:0001HW.C205BA3500C4CAEEF01826C8(a)news.sf.sbcglobal.net... >I want to turn on 4 lamps in 6 combinations. These are controlled by 3 > switches in 6 corresponding combinations of contact closings. > > The truth table looks like this > > Switches Lamps > A B C W X Y Z > ----- ------- > 0 1 0 1 0 0 0 > 0 1 1 1 1 0 0 > 1 0 0 0 0 1 0 > 1 0 1 1 0 1 0 > 1 1 0 1 0 0 1 > 1 1 1 1 1 1 1 > > While it's straight 3-bit binary count input, how to I translate it to the > desired 4 output combinations? What's the best way to implement such an > input-to-output matrix? > > Input from switches is 12 vdc and output requires 12 vdc, milliamp drive. > > I'm ignorant in all things PIC, so prefer to have another solution. > > Ideas? > -- > John English > What's wrong with relay logic, apart from the cost? No input or output interface problems, (potentially) no PCB needed, no electronics! Graham Holloway (Electronics Designer) |