Project Summary
Build yourself a single shot Pic Micro Controlled by stable Relay FEATURES 1. One touch activated for on or off 2. Open connections for other sensors 3. 10 -12 volt operation 4. Led indicators for on off status 5. Can be Rf controlled 6. Can be serially controlled 7. All code Flow charts included 8. All circuit boards layouts, schematics, c code, precompiled hex files included
Project Description
Circuit Description
The circuit comprises power supply section CPU section and relay driver section The power supply section comprises D4 ,D7 which form reverse polarity protection , R6, D3, C3, D3 Q2 and C7
D3 provides voltage stability at 5v6 with R6 supplying base current to Q2 . C3 decouples the base of Q2 Finally C7 ensures extra ripple rejection
U1 forms the cpu component who’s sole function at present is to sense switch detection on a logic low i.e. zero volts via a momentary action push button switch, held to 75%, 85% of the supply rail via R4 being the 5 volt feed to the input GP3
During this process U1 programmatically behaves as a one shot bi stable i.e. two states, either on or off and effectively does away with older RS flip flop types of integrated circuits e.g. CD 4013 etc
Once logic state detection occurs subsequent output appears on the GPIO port, GP0 for the relay to engage simultaneously illuminating D1 via R2. D6 , GP2
R1 and D6 supply the base of Q1 , the latter component i.e. D6 ensuring that we provide some type of protection in the event of Q1 failing base collector short circuit R3 forms a potential divider in conjunction with R1 and D6
Off state is indicated via the R5 D2 GP1 and is illuminated to illustrate such state
D5 and C2 provide decoupling and back EMF protection for Q1 when relay is energised de energised
Finally C5 and C6 form extra decoupling to illuminate noise of the supply rails both 5 volt and 12-14 volt rails
Switched 12 to 14 volts is done by RLY1 one end of the contacts being directly connected to Vin
The circuit board is constructed in the normal manor utilising Proteus professional to layout tracks on Printed circuit board
Before you start clean the board thoroughly My own method is such you may possibly have a different method entirely
Polish the copper clad board with Brasso and a lint free cloth Don’t overdo this but just try to get a reasonable mirror finish in one or two attempts
Print the PCB drawing onto press and peel transfer’s rough side using a black and white laser printer
Placing the rough side i.e. the side you printed onto firmly on the copper clad board
Setting the Iron temperature to approx half way and holding the sheet of press and peel carefully and in position on the copper clad board
Place the iron on top of the press and peel, “Shiny side facing upwards”, and wait for press and peel to adhere
Check the press and peel regularly by lifting the iron and observing the changing colour of the press and peel “You should see the tracks that you printed onto the press and peel becoming darker “ Near enough Black indicates job is complete
Turn up the iron slowly to about 3/4 of the way whilst doing this no further otherwise press and peel melts
For more detail: Single Pic Micro single shot bi stable Relay
