Instructables

RC CAR (Parallel port interfacing)

Step 2: Getting started (Hardware phase)

Hardware phase
                              first of all open the remote of the Rc car. You will analyze that there are four switches. when we press the button each switch is closed.. Before pressing the button turn on the remote and check the voltage across the terminals of the switch  it should give a value.. after pressing the switch hold the button and check the voltage it should show zero..

this concludes that our remote is working on short circuit technique. that is if there is a voltage across the switch and when its pressed it is short circuited.

Observe that one wire is common in all the switches its the ground of the circuit. which concludes that we need to solder five wires in the remote. one for each switch and one for ground.

it can be checked that when u short the ground wire with any of the switch wire the car performs the action of the switch who's wire is shorted if all the four functions are performed then it means u have picked the right ground. and the right switch wires.

here are the pcb design and the simulation of the circuit for interfacing (download parallel port circutary)
 
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a7la nono1 year ago
i have different remote there is one switch inside how i can work in this remote i means how to connect four wire in one switch

this is my remote from behind
http://im20.gulfup.com/VQJ41.jpg[^]

http://im14.gulfup.com/Y6wh2.jpg[^]


also i have another remote i think there are four switch but i'm not sure
if this remote 4 button can you explain how to connect 4 wires
http://im28.gulfup.com/jLRV2.jpg[^]

remote from behind
http://im20.gulfup.com/XkL32.jpg[^]

usbg3rd (author)  a7la nono1 year ago
here is the edited image ."s" is marked red and the naked wires are marked green
ed.png
(removed by author or community request)
you means to connect 2 wire from S with (BJT emitter) AND 2 wire from " green arrows" connected with (BJT collector )