The simple 555 generator

The 555 generator is a super cheap solution to my problem. I needed to test a counter and was financially limited. The frequency didn't have to be accurate, anything better than pushing a button to get impulses was OK. This "generator" has 4 sets of frequencies :

JP3 is a button used to switch the device on and off. The power supply (anything from 4-12V) is connected onto JP4. JP2 serves as the output for the signal with an ateunator, if we don't need the full strength (voltage) of the signal, only, say 3V of 5V. We can set the output value by R2. JP1 gives the full strength of the signal, with a current depending on the 555 type you use. R3 is used to set the frequency within a range chosen by the DIP switch S1.
You can set which range of frequencies you want to use with a DIP switch. With it you enable or dissable a capacitor which is hooked up into the datasheet cuircit of the 555 chip. Here's the schematic:

And the photo of the device (kinda suggests how to do the mechanical part):

I published this in a Czech electronic newsletter. You can download the article here: [DOWNLOAD]

Here is the board and the schematic in Eagle format: [DOWNLOAD]