automaticly shorting circuit

roboticmehdi

hi everybody. i need a circuit which will short 2 cables for 0.5 seconds every second. let me explain like this:

_______________
(+2.4v) | | (0)
-----------| |--------------
| |
-----------------

in the ugly drawing above you can see two wires with a potential difference of 2.4 volts connected to a box. the box just represents the circuit that i want to make with your help.
this box must have zero resistance for 0.5 seconds and infinity resistance for 0.5 seconds. so its like a pulsating current with 1Hz across this two wires. Can you guys help me with this ? i have circuit elements like resistor, capacitor, leds, transistors(only BDX53C, BD243C, TIP41C and BDX54C), and etc... The timing doesnt have to be so strict, 0.5s+-0.05 is fine. The current that will be drawn during shorting is not high, not higher than 100ma. I need the simplest and most efficient circuit that you know :)

roboticmehdi

sorry about that drawing, it didnt come out like i wanted. here is correction:


2.4v ----------------|BOX|--------------- 0

Bassalisk

Simplest?

Put BD243C npn transistor across those cables(collector to 2.4V side). Use a 555 timer for sending square wave pulses to base.



Here are the values for 555 timer.

mdjensen22

You could always drive a little reed or telecom relay if desired. Those are pretty quick and will give as close to a dead-short as you can get.
The 555 timer circuit above should be able to drive one of those without issue.

darkwood

If you suspect you may need to alter timings etc and dont mind spending a few extra pounds you con get a simple logic controller with relay outputs, a basic logic programme will give you an unlimited output function with easy alterations and time scaling down to the thousands of a second.
You can get a starter kit and i promise you, you'll have programmed it within the hour even with no experience, the best thing is you can save the programme and load a new one for your next project.