As an update to this thread, I have now identified the use and component connected to the Lens contacts
For those unaware, the camera requires a lens to be connected that is identified to the system via its two gold lens contacts. If a suitable lens is not seen by the system, the aperture wheel moves to protect the microbolometer so the camera cannot be used.
I was recently contacted fir help with an IR TCM 384 camera that does not have a lens. I had already considered the possibilities when it came to the use of the lens contacts…they were…
1. Temperature measurement of the lens using Thermistor, Thermocouple or simple silicon diode.
2. Lens identification using some unidentified 2 connection IC
After some simple tests I discovered that the resistance across the lens barrel contacts was in the Mega-Ohms in both directions but it did display a 0.6V reading in diode test mode and and an O/C in the opposite polarity. This suggested to me. That I was dealing with an IC of some sort. The obvious possibilities were a temperature measurement IC or an ID chip.
There are only 2 contacts in use here as the lens barrel is not used as an electrical pathway. I immediately thought of the common Dallas iButton units that use only 2 wires for data I/O operations. The 1-Wire system is used for this. The possibilities remained if either a temperature sensor or ID chip but the owner of the lensless IR-TCM 384 read the user manual that I had provided and highlighted that the camera was able to identify the exact lens that is fitted, whether it was the serial number against which it had been calibrated and whether it was even the same lens type. Suddenly, lens ID became the more likely use of the contacts.
As luck would have it, I purchased a couple of Maxim 1-Wire serial communications adapters on eBay a few years ago. I was looking at 1-Wire systems used on laptop batteries and the Maxim adapters were very cheap so added to the “may be useful some day” stock in my lab
I dug out the two serial 1-Wire adapters and an iButton that I had and tested the Maxim 1-Wire viewer software on a laptop that is equipped with a real serial port (not a USB to Serial adapter) The setup worked perfectly and read the iButton with ease. My iButton was an eeprom and I suspected the lens ID chip would also be an eeprom of some sort, likely with very small memory capacity.
I tested the iButton with my multimeter in diode mode and saw the exact same 0.6V / Open Circuit readings as found on the lens barrel. This gave me the correct pin out of the lens barrel connections as well. Using a couple of jumper wires I connected the 1-Wire interface to the lens contacts and was immediately rewarded with the unique ID number and the device type identification of the 1-Wire IC within the lens
The device was not the eeprom that I had expected to see, but rather a DS2406P 1-Wire 2 output switch ! That surprised me so I quickly downloaded the data sheet. Whilst I cannot explain the use of a 2 port switch in the lens, I did find that that DS2406P also contains a user programmable OTP EPROM of 1Kbit in size
This was what I was looking for as it would likely contain data unique to my lens.
https://datasheets.maximintegrated.com/en/ds/DS2406.pdfUsing the Maxim 1-Wire viewer software I was able to display the contents of all of the DS2406P data areas so could clone the IC if required. The switch function could potentially be used in some lens versions to select an electric lens cap or even change the FOV setting on a multi FOV lens. My lens does not appear to use this function though.
More from me on the data that I found inside the lens in the next instalment.
My thanks to the owner of the lensless IR-TCM 384 for focussing my attention on the cameras lens contacts again as they had long dropped off my ‘Radar’ as I have the original Jenoptik lenses to use with my cameras.
Fraser