NE555 Duty Cycle 50

324

04:53:51

The NE555 with a 50% duty cycle and a frequency of 1kHz in this configuration can also be used (with a few changes) to do a metal detector. 
If you want to keep the 50% duty cycle but change the frequency you can use this equation R*C=1/(2*f*ln(2)) keep in mind that the resistence value that you find with this equation is the same for the two resistors (if the resistors are not the same the duty cycle will change) and that the capacitor in the formula is the 470nF capacitor  in my schematic, don't replace the 10nF capacitor.
Metal detector circuit coming soon.

published 9 years ago

thebugger

9 years ago

How exactly do you plan to use this in a metal detector? These kind of circuits are usually hard to make and callibrate.

SkeLe

9 years ago

I'm tinking on it but i think that is possible to make it

thebugger

9 years ago

Metal detector work like this. First you have a stable oscillator stage at let's say 1Mhz. Stability is achieved with a crystal oscillator. Second you have another 1Mhz stage (they need to be in exact synchronization). The second oscillator is not a crystal one though. It's a Hartley or a colpitts oscillator. It consists of a large coil that acts as a senson. See this is what happens. At first the oscillators are at sync. Once the coil comes by a metal the frequency of the second oscillator slightly shifts. The difference is then compared and producea as the beat frequency. The higher thw pitch the more disruption on the coil thus a larger object.

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.