555 timer chip and arduino uno

Hi all

Was just wondering if anyone had ever used a 555 timer with the arduino. I am looking for advice on taking a signal from the 555 to let the arduino know that it had been triggered as in a light detector for example. Can a link to the output pin be used?. My concern is that the output can deliver 200Ma. What would the limit of the arduino be in regards to current inpuit?

Many Thanks


There should be no problem with this, assuming that the voltage is correct. The 200mA is the mac the 555 can deliver.


Thanks Holmes4, My concern was risk of damage to the arduino input with the 200ma from the 555 output.

Yes this is safe to do provided you are running the 555 from the Arduino 5V supply. But is there a reason why you want the light detector to trigger the 555, instead of triggering the Arduino directly?

Hi dc42

yes, what I wanted to try as a learning curve was to use a board I made ages ago using a 555 as a light detector and run as is as it works fine, but, I wanted a signal sent to the arduino to display an input response to notify me that is was infact detected as getting dark. I thought that linking the arduino to the trigger or output in ( pin 3 ) of the 555 would maybe work.

Yes, you can run the 555 fromm Arduino +5V and connect pin 3 of the 555 to an Arduino digital input.

Just for comparison, you could replace all that external hardware with a simple light dependent resistor connected to an analog input.

Thank you very much for your help guys, much appreciated. :)