Missing Pin detection test unit

Thread Starter


Joined Oct 24, 2013
I need help in designing a circuit to test for missing connector pins

Unit to test is a 25 pin molded connector, I have built a test box and installed 25 spring loaded test probes that align with the connector pins
the switch probes are normally open until compressed then conduct current through to the bottom socket of the probe where I have attached a wire to each one, My idea was to send 24v to the first switch probe if it is compressed that means the pin in the connector is present and will allow the current through the attached wire to a relay switch then back up to the next switch probe and next relay switch and on through all 25,
pins.... if all pins in the connector are present the current will continue through to activate two solenoids one that allows the lid to open and one that will do a punch to mark the part as tested, and also lite a led as a
pass test... if the test fails that would mean a pin is missing in the connector and the lid latch will stay locked till a override key allows the lid
latch to open.... As I am more mechanical then electronic I could use all the help I can get... I can send pictures of the mechanical unit I have built... <SNIP>
Last edited by a moderator:


Joined Jan 21, 2013
It sounds like you've got it fairly well thought out, is there anything specific you need help with.

BTW, you can upload pictures to this thread by attaching them to a post.

Thread Starter


Joined Oct 24, 2013
Thanks for the reply, I am concerned weather once the current flows through all the switch probes that I will have the amps to operate the selonoids do I have to add a timer relay to hold open the lid latch long enough for the operator open the lid, right now I have a button switch on the base plate that activates the operation once the lid is shut... I'm afraid that the selonoids will activate to quickly when opening and shutting the lid...?


Joined Apr 24, 2011
How can you upload a picture....its asking for a url for the image...
Hit the "Go advanced" button and look for "manage attachments." That lets you upload a thumbnail of your pic that links to your full image.

What many of us then do is use the ULR of the link to insert the full pic into the post.

Like so: