ControlIR-2000B broken chopper wheel - Page 1
Forum section: electronics / general

author: notnup
author_rank: Newbie
timestamp: January 05, 2025, 03:04:13 am
content: Hi EEVblog community!I recently picked up two Raytheon ControlIR-2000B security cameras from eBay, and I could use some help with one of them. While I managed to fix a harness issue on the first camera, the second one has me stumped. After opening it up, I discovered some broken pieces of what appears to be the "chopper wheel."Would anyone know if this part can be sourced somewhere, or is this camera beyond repair? I'd love to get it working again if possible.Thanks in advance for any help! Really grateful to finally be participating in such a knowledgeable community.Best regards

author: Fraser
author_rank: Super Contributor
timestamp: January 05, 2025, 01:23:05 pm
content: That is a major problem as spare solid chopper wheels are not available.Options are:1. Collect together the parts of the broken chopper wheel and reassemble it with a suitable adhesive designed for ceramics and glass.2. Buy a standard plastic frame type chopper wheel from Bill_W on this forum and use that in place of the solid type.3. 3D print a chopper wheel as previously detailed on this forum.Fraser

author: hap2001
author_rank: Regular Contributor
timestamp: January 05, 2025, 01:40:30 pm
content: Why yours chopper look like glass? All my BST cores came with thin plastic film choppers.

author: Fraser
author_rank: Super Contributor
timestamp: January 05, 2025, 02:42:18 pm
content: Hap2001,That is the later chopper wheel design, as used in the Honda thermal night vision system for cars. It is just a development of the plastic framed film type chopper wheel. It does not suffer age related degradation. It will be made from either germanium or possibly silicon (silicon has more transmission loss though).Fraser

author: Fraser
author_rank: Super Contributor
timestamp: January 05, 2025, 03:13:18 pm
content: Notnup,You can purchase the original plastic frame and film type chopper wheel here….http://www.fire-tics.co.uk/spares.htmIt is a bargain for this very rare spare part at only £18. Bill_W is a really good chap for offering these spare parts for sale.You will likely need to modify it a little to fit your camera, but nothing very difficult or dramatic. The centre boss spindle hole will obviously need increasing in size if your motors spindle is larger diameter. You will also need to make sure that the “phase and rpm” optical sensor slot in the plastic frame outer edge is in the same position to your solid wheel in relation to the opaque spural.Fraser

author: notnup
author_rank: Newbie
timestamp: January 05, 2025, 04:06:57 pm
content: Hi Fraser,Thanks for your detailed help. I think I'll start by attempting to rebuild it, then try 3D printing (I haven't checked for any STLs floating around?). If those options don't work out, I might try to get one of the ones from Bill_W's shop.I'll keep the thread posted with how it goes.notnup

author: Fraser
author_rank: Super Contributor
timestamp: January 05, 2025, 04:58:40 pm
content: Sadly the 3D printable chopper wheel on this forum is designed for the Cadillac De-Ville Raytheon core and that uses a different spiral shape to what you need.https://www.eevblog.com/forum/thermal-imaging/raytheoncadillac-deville-camera-3d-printable-focusing-mod-and-chopper-wheel/This thread may give you some ideas though…..https://www.eevblog.com/forum/thermal-imaging/argus-3-(bst)-teardown-and-repairs/

author: notnup
author_rank: Newbie
timestamp: January 05, 2025, 08:47:22 pm
content: After examining the pieces, I have concerns about achieving sufficient structural integrity for the required RPMs, even if I manage to glue everything together. However, I'll do my best to make it work. I'm planning to 3D print a supporting brace to help keep all pieces level and aligned, especially since removing the remaining wafer for installation may not be possible with the current mount.I'd like to verify my understanding of the chopper wheel's function: The wheel allows partial transmission of infrared light, while the laser-etched curved pattern creates a sweeping motion across the focal plane at a specific rate, synchronized with the motor. This pattern helps establish a reference point for the sensor. The germanium material is chosen for its superior infrared sensitivity.While a plastic replacement wouldn't offer the same infrared transparency as the original, I'm wondering if this transparency feature might not be essential for basic operation. Is this thinking correct?notnup

author: dennis1573
author_rank: Contributor
timestamp: January 05, 2025, 10:16:55 pm
content: My idea for gluing the Chopper wheel together, is a 3d printed Ring around it. You put some glue inside it, and that will hold the 2 pieces together.That way, you dont need to put glue onto the Chopper wheel itself and it will also remain perfectly balanced.You could also just print a new one of course. There is a Chopper wheel design i made in the second Link Fraser posted.I designed it for the Argus 3, but judging by the Picture you posted it looks like the Timing notch in my Design is already in the right spot so no adjustments needed.But the center hole might be to big, because on the Argus 3 the chopper wheel is screwed on. So you might need to edit the design slightly...But i would suggest, you try to repair your Chopper wheel first.I have a few Cameras with the Germanium/Silicon Chopper wheel, and i think the performance is much better (much less Noise and better Contrast).i have attached an .stl of my "Repair ring Idea".i quickly measured the Chopper wheel in my Camera, so this should fit. I have also added a cutout, for the timing hole.But remember, its just an idea it might not work.Good luck with your project :-)EDITI didnt see, that you already had that idea...i have attached another Version: "Chopper_repair_ring_v2" with the 4 radial supports added.As Fraser said, it wont be visible and will probably give it a bit more strenght.

author: Fraser
author_rank: Super Contributor
timestamp: January 05, 2025, 10:57:13 pm
content: Notnup,You asked about the theory behind the chopper wheel……The BST FPA pixels react only to changes in illumination. Without a chopper wheel the camera must be kept in motion for the thermal scene to be created. The chopper wheel uses a carefully designed spiral of thermally opaque, or semi-opaque, material to create a sweep across the FPA that returns the swept pixels to a ‘baseline’ state ready to be illuminated by the thermal scene. A change in the pixels is thus created. The chopper wheel spiral must be synchronised with the readout of the BST FPA for correct operation and its position is detected by the optical gate that is visible at the edge of the wheel.The early chopper wheels that were used on Pevicon tube cameras used a spiral made from thin fibreglass material. The BST chopper wheels used the transluscent film in a frame and the spiral is printed onto the film as a pattern of dots. The spiral is semi- transparent to thermal energy. So the chopper presents the BST Sensor with a high transmission material with a lower transmission material sweep across its face to ‘reset’ the pixels to baseline. This was done to compensate for the BST pixel technologies relatively low dynamic range. A thermally fully opaque spiral may be used but the camera will have reduced dynamic range. In many common use scenarios, this is not a problem.If you look at the plastic frame of the standard chopper wheel, you will see that there are 4 radial supports for the film. These do not adversely effect the performance of the camera and the cracks in a repaired solid chopper wheel will likely be unnoticeable in operation. I understand your concern about rebuilding the solid chopper wheel. The suggestion by others to use a supporting frame/rim is an excellent idea. I would try to repair the solid disk before accepting the lower dynamic range provided by a fully opaque spiral chopper wheel.Fraser

author: Bill W
author_rank: Super Contributor
timestamp: January 06, 2025, 12:30:24 pm
content: The image processing maths behind the chopper is that each pixel sees :Focussed image + nonuniformitythenLocally averaged image + nonuniformityon alternate fieldsThese are then subtracted, with a grey level bias added, to give (Focussed-average+grey) all the time.That is why BST images have the 'halo' around hot objects, it is a physically generated large aperture unsharp mask.If you can't fix it, yes I still have some chopper wheels left, either 'OK to use' or as frame / slot donors for DIY.Note fire-tics is not a 'shop' it is a shop window. I have not set up click to buy or any of that functionality. Send me an email (or PM here), I check the item, you pay me direct by paypal & I post it outBill

author: Axiomader29
author_rank: Newbie
timestamp: January 23, 2025, 03:45:32 pm
content: I have a 2000B that I’m working on now. My chopper wheel wasn’t spinning at all. I ended metering the board pinouts for the wheel, while it was removed, for current and voltage, (4.88 volts, 1.65A) Then bench tested the wheel on a regulated, adjustable power supply, it spun up just fine. However, when I connected the chopper back to the main board and powered it up, there was no voltage present? I cleaned the optical sensor and tried to manual spin the chopper wheel, and it began to spin, very slowly. Can someone tell me what the correct rotational speed should be observed? Are the rpm’s variable? I am getting an image now on the video screen, but only a primitive outline, or when I actually move in front of the camera does it make out any worthy details.Video Link:https://imgur.com/a/SeVthnf

author: Bill W
author_rank: Super Contributor
timestamp: January 24, 2025, 12:11:56 am
content: Quote from: Axiomader29 on January 23, 2025, 03:45:32 pmIt is phase locked to the video frame rate so should be a constant 30rpsAttached is from an Argus2 where we had the sensor in a different place hence at a different time with respect to the video, but hopefully you get the idea.Standard setup I think the pulse is at field sync time