Dear Community,
I need a possibility to control this shutter https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=8406 via an external 5V TTL. I want to open the shutter for 0.5, 1, 2.... sec.
Thank you very much for your help.
What Arduino experience have you got ?
Will there be a sequence of shutter openings of fixed times or will the user set the open time in some way ? If so, how ?
I don't have any experience...
I want the user set the open time in some way
The first thing to do is to get to get some experience by trying and understanding the examples in the IDE unless you want to pay someone to write it for you.
Do you have an Arduino ?
Have you installed the IDE ?
I want the user set the open time in some way
User interface is often the most complicated part of the project. What are your ideas?
Will there be a laptop or computer available?
Do you want to use a mobile phone?
Do you want to build a control panel with switches for different times settings?
There will be a computer a available.
There will be a computer a available.
That's good. You can use the Serial Monitor of the IDE to communicate with the Arduino connected through USB and make the settings. It is the most simple method.
Do you have an answer to UKHeliBob's questions in post #3? Getting started with the basic examples and becoming familiar with the environment will be your first step. Having the Arduino control the shutter through the controller unit will be very simple. If you can blink the on board led, you can blink the shutter.
In terms of the specific shutter program, start with the design the interface. No code required. Do you want to set up the exposure time , number of exposures, time between exposures? Different exposures during a run? A command for start? You will set up the program to prompt the user to enter data--What do you want the prompts to be?
When you know what information to enter through the monitor, the next thing to do is to review Robin2's tutorial on Serial input to the Arduino Serial Input Basics - updated - Introductory Tutorials - Arduino Forum
Thank you for your answers. 
I don't have any hardware. What should I buy? Then I will familiarize myself with programming
I don't have any hardware. What should I buy?
Arduino UNO.
You will also need a coaxial cable to connect to the TTL input of the shutter controller. I don't know if it comes with the controller or not.
You will have to modify one end to connect to an output pin and ground of the arduino but that will be straightforward.