But how is that possible?
The IC is in the correct place according to the print...
The notch on the IC is right above the notch from the IC socket and right above the notch drawn on the print itself.
And according to the instruction in the manual it's also mounted correctly.

Still, I tried turning it around, in which case te entire kit doesn't do a thing.
So I turned it back and in that case it's still the same going too fast first and then suddenly stopping.

 

Pin 7 measures exactly the same voltage as C3...
Which means there's a problem with the (installation of) the NE555?

Yes. Replace it. You have it installed correctly, but for some reason pin 7 isn't going low.

 

Okay, I'll pass by the store tomorrow and buy a new one.
I hope that solves it.

 

But how is that possible?
The IC is in the correct place according to the print...
The notch on the IC is right above the notch from the IC socket and right above the notch drawn on the print itself.
And according to the instruction in the manual it's also mounted correctly.

Still, I tried turning it around, in which case te entire kit doesn't do a thing.
So I turned it back and in that case it's still the same going too fast first and then suddenly stopping.

I'd momentarily gotten confused on which way you had the board oriented in the bottom photo; I realized moments after I posted that you did indeed have the 555 timer installed correctly from the beginning; so I deleted that post - obviously, not soon enough. Sorry about that.

OK, on the 555 timer, what do you measure (using ground as a reference) on pins 1, 4, and 8? 1 should measure the same as ground (0v difference), 4 and 8 should measure the same as the cathode side (banded end) of D3.

If the LED is constantly illuminated, the NO to COM connection should be closed, and the NC to COM connection should be open.

 

Basically, if pins 1, 4, and 8 on the 555 timer are measuring correctly, and pins 2 and 6 measure the same as the voltage on C3, the 555 timer is bad.

 

No problem, I get confused sometimes too, probably a lot more than you

This is what I measure:

- pin 1: 0.00V
- pin 4: 10.65V
- pin 8: 10.65V
- cathode of D3: 10.65V
- pin 2: 7.07V
- pin 6: 7.07V
- C3: 7.07V

Well, I guess that's pretty conclusive then...
The NE555 is bad, I'll replace it tomorrow.

If the LED is constantly illuminated, the NO to COM connection should be closed, and the NC to COM connection should be open.

This is indeed the case.

 

Do you happen to have a spare 20k resistor (approximately) available? Anywhere between 15k and 27k would be good. If so, connect it between pins 5 and 1 of the 555 temporarily. That should lower the control voltage, and may cause the circuit to start working.

 

No, I don't have that available.

 

I just changed the NE555.
It still behaves the same, the problem must be somewhere else.

 

Interesting.
Did you happen to pick up a 15k to 27k resistor, or do you have a pot that could be set in that range? If so, connect it temporarily across pins 5 and 1.

 

I took a look at your solder joints, and I found some that might need some rework. Se picture. I do not know if it will help but you can try it

 

The closest one I have to that is 33k...

 

There is a possibility this little solder bridge might be the culprit. Check and see. It's located under the pot on the right side.

 

Here is the Velleman forum, you can go there and ask for advice, etc....
http://forum.velleman.eu/viewforum.php?f=5

 

I don't know why, but it started working all of a sudden.
After it's been on for about a minute it just starts functioning normal now.

 

Here is the Velleman forum, you can go there and ask for advice, etc....
http://forum.velleman.eu/viewforum.php?f=5

I had already tried the velleman support forum,
but I recieved more help here in couple of hours than on the velleman forum after a few days.
And since I need my project to be finished by sunday, I couldn't wait very long.