Mk125

Kits Mini Kits Range
1

Hi,

I am using the MK125 kit to detect whether a UVC bulb is working or not (so that a user doesn’t need to look at the bulb.) I have two products built with the kit so far and both don’t work. One of the kits was working OK to begin with but soon failed. Failure mode is; the sensor is not detecting the light even although it is on. We have the pot set to read 1V between pin 13 and ground. Please can you suggest what may be wrong.

The LDR is situated in a very humid atmosphere. Is it possible that it could be damaged by water ingress or affected by condensation? Finally do you have any datasheets on reliability of the product / LDR?

Regards,

Fergus

2

If the kit worked at first and now it stopped working, then the problem is very likely caused by a meachanical cause. The LDR is not waterproof. You should take proper care when using electronic circuits in a humid environment.

3

Thank you for your reply. The kit worked to begin with on one kit, but didn’t work at all on the other. Does the voltage setting between pin 13 and ground seem reasonable to you? We have the LDR situated remotely from the rest of the circuit board, only the LDR is in a humid environment. I am going to try replacing the LDR and covering it with clear silicone to protect it from the humidity. Do you think it will still work through the silicone?

Thanks for your help,

Fergus

4

1V at pin 13 is a possible value.
LDR will still work but RV1 will probably need adjustment due to sensitivity change.

5

Hi Again,

I have checked through previous posts for the MK125 looking for replacement LDR’s and found that you specified “Velleman LDR04”.
Would you be able to advise where I can buy the LDR only. I am using Rapid Electronics to buy the kits.
Do you have any datasheets available for the LDR?
If not could you tell me what the operating temperature limits are?

Best regards,

Fergus

6

Incidentally, I have run a test using the LDR smeared in clear silicone adhesive in our humid environment for 3weeks now without failure. Thought you might like to know…

7

I knew it did not like humidity…

8

Hi,

Please can you advise me on my questions from my earlier post yesterday?

Thank you,

Fergus

9

Sorry, no datasheets or specs.
As for a distributor, any Velleman is able to order a sensor for you, however, I doubt they will order one piece.
Basically, any LDR will do the job.