• Author:Ralf
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Making clicking simple

TEDxMünster has never been as big as it will be this year. That means the venue is bigger but the stage and the technical team have never been so far away from each other. This could be a problem. If you are giving a TEDx talk, you won’t be able to give a signal to the technicians for the next slide to appear. What can you do? Lukas, our team technical whizzkid, also a mathematics student had an idea. Nils, also on our team and communications student talked to him about his idea. They discussed how difficult the path from idea to solution can often be and why it’s not always bad if something goes wrong in the process.

Lukas, can you explain again: what is the problem actually?

The problem is the distance between stage and the technician’s room. We have to bridge 150 meters, a cable line is out of the question so we have to solve it with a radio signal. This signal has to be converted into a keyboard input, which will then go into the computer.

So that then the next slide appears on the screen with one click.

Exactly. We want to it to function like a keyboard, one click to move to the next slide on the screen.

Is there nothing suitable which you could just buy?

Yes, but the devices are very expensive. Besides I thought to myself: why should we spend so much money if you can just build one yourself?

What would such a thing cost?

I would say at least about €200, that probably doesn’t even include a receiver! With a receiver, the price would probably go up approximately € 300

And how far have you got with building your system?

I’ve got quite far but I still have a long way to go. To be honest, it’s already cost me some time and energy!

How have you gone about developing your idea?

I’ve been thinking about different solutions for quite some time. First, I had got myself a micro-controller, but I didn’t really know how that one worked. That’s why I decided to do something different, and that all took a while. I used a Raspberry Pi for that.

What is that?

A small computer with about the size of a pack of cigarettes. The computer is running a Linux distribution and it recognizes keyboards. I use it together with a conventional presentation remote control. Modern devices send signals to the computer, and they all kind of pretend to be keyboards. That’s a technology that fits my needs. If you know a little bit about programming, you can adjust the devices quite easily. The signals are then forwarded to the receiver, which types them in virtual.

Then the problem could be solved quite easily?

Unfortunately, not. That was the solution I used last year, when TEDxMünster was in the castle of Münster. I was able to install a LAN cable from the stage to the technician’s room. Unfortunately, a cable is not an option this year.

What does the alternative look like?

Two months ago, I started to work on micro-controllers.


In theory, it works quite well! I already had a prototype but then I accidentally connected the thing to an eleven-volt power supply. Unfortunately, it is only built for up to three-volt. That means: I blew it up. Then I bought myself a new controller. Two weeks later I noticed that I also killed my programming device. So, I also needed a new one of those, and then I thought I had a solution.

But you hadn’t had one?

Exactly. I had to get the keystrokes back to the computer somehow. The microcontroller couldn’t emulate a keyboard. But oh, that’s way too complicated to explain in detail! I tried it over another part, then I soldered everything together. After that nothing worked at all. I took everything apart again, wrote e-mails to acquaintances, asked a lot of questions, experimented a lot. At some point I had a radio connection – but only over five meters. And then I lost motivation.

That means the project failed?

No, I still have a plan B. I have a new microcontroller. It can bridge 200 meters. That means I have a new wireless chip, a new microcontroller with a bit more hardware.

What does it do?

It can, for example, transmit right through our house through various thick walls without the signal losing any of its strength. Programming the thing was also a challenge, but in the end, it worked! Anyways, everything is now half-finished in my cellar. Now all I have to do is to solder the rest together.

And that’s the final solution now?

Let’s put it this way: I have a good feeling that the whole thing will work in the end. The frequency has changed once again, but that can probably also be solved.

Why is the frequency so important?

There is a rule of thumb: the smaller the frequency, the further you can transmit. You know that from the radio. And the less the frequency is going on, the further you can transmit.

What does that mean to you?

There are several possibilities. I could try it over WIFI at 2.4 GHz. This has the advantage that the WIFI connection is very stable. The disadvantage is: WIFI is everywhere. Then there are various other frequencies in question. There may also be other problems. For example, it could be that the radio microphones in the theater would interfere the transmission. I don’t think that this should be a problem, but you never know.

What would happen if this would be the case?

Well, then there would be an interference, but I also have a plan C. I could replace the LAN connection with the cable from last year with a WIFI connection. With a few tricks you can also bridge longer distances.

With which tricks?

You have to make sure that there is as much air as possible in between the signals. Also, no people – they also absorb radio frequencies. So, I got myself a WIFI stick. I will put it in the Raspberry Pi and see how far I can get with it. If that were 100 to 150 meters, I’d think it was great. I am curious myself!

So, to summarize: there are three solutions?

Yes, but the first option basically is out, it doesn’t really work anymore after I blew it up. Then there is the second one which I could screw together with the necessary hardware on a weekend. For this, I need two Raspberry Pi devices and a WIFI network. And then I also have my plan B in which I will solder the remote control together. I tested it already at our last rehearsal. I was able to transmit the signal right through the auditorium. But, of course, I prepared both to make sure that at least one version will work on 2nd November in the theater.

Financially, it would probably have been worth it to buy a ready-made device, right?

Well, if you only look at the numbers, it could be. But I wouldn’t have learned so much, and the knowledge might help me to solve another problem in the future!

Lukas Bröring