flat intercom CRT - Page 1
Forum section: electronics / projects

author: rollatorwieltje
author_rank: Unknown
timestamp: March 03, 2014, 06:11:53 pm
content: For a project I'm looking for a flat display. However, it should look a bit "vintage", so I thought one of these flat CRT displays would be perfect.I don't really want to build my own CRT driver, so I would get one of those intercom phones and use the guts from that. They all seem similar in construction, using 2 wires between the camera and display.I suspect these things just accept composite video, as some claim that you can view the image on your TV as well. There must be some extra signals though for the doorbell and 2 way audio.Has anybody hacked one of these things? Does it accept composite video?

author: David_AVD
author_rank: Super Contributor
timestamp: March 03, 2014, 09:14:50 pm
content: As far as I know it is a standard NTSC or PAL format on some of them. The power, audio, call signal and video are mixed onto the pair of wires going to the door station. You should be able to find a point in the monitor where the video is split off however.

author: nctnico
author_rank: Super Contributor
timestamp: March 03, 2014, 09:22:15 pm
content: Or they use a solution with seperate wires for signalling and video. These things are low tech and cheap so they should be easy to hack.

author: weirdal1968
author_rank: Newbie
timestamp: March 04, 2014, 11:36:46 pm
content: That looks suspiciously like they grafted some kit onto an old Sony Watchman "lollypop" CRT. I'm pretty sure the Sonys have a video in or at least an internal composite video input point.FYI they made Watchmans in a few sizes including a Mega Watchman. Just remember that CRTs are fragile and require high voltage to operate. Since the CRTs are small the shock wouldn't kill you but human bodies react unpredictably to impromptu muscle stimulation.

author: rollatorwieltje
author_rank: Unknown
timestamp: March 06, 2014, 06:46:14 pm
content: So I got one for a little too much money on Ebay... An Elro VD53A. Oh well, I could just use it for it's intended purpose if it doesn't work for my project, the camera actually works surprisingly well in low light conditions. It even has an alarm button so the outdoor unit will start to make a horrible noiseThe CRT is quite a lot bigger than I expected. It was advertised as 4", but it turns out they were actually honest, the visible area is indeed 4". I sort of expected the tube to be 4"The HV section is well protected, it's all inside a metal can.It has an actual IC for the ding dong sound, aRT0302CMOS design for door bell application.It draws 0.54A at 13.5V, the power brick (judging by the weight a transformer based thing) is rated for 13.5V 1200mA.edit:well that was disturbingly easy, the cable from the control board to the display board was even labeled. I'm using an Arduino Mega with theTVOut library.

author: SeanB
author_rank: Super Contributor
timestamp: March 06, 2014, 09:34:37 pm
content: So you are making a HUD, be nice to see the finished article. Are you displaying direct or are you going to use a glass reflector.

author: David_AVD
author_rank: Super Contributor
timestamp: March 06, 2014, 11:14:06 pm
content: Quote from: rollatorwieltje on March 06, 2014, 06:46:14 pmWell, the tube neck and defection coils need to go somewhere.They are beside the viewing area instead of poking a few inches out the back.

author: rollatorwieltje
author_rank: Unknown
timestamp: March 08, 2014, 03:00:09 pm
content: I noticed something funny, this CRT is extremely sensitive to magnetic fields. Of course CRTs are sensitive to magnetic fields, but I've never seen it this bad. Just touching the glass envelope also distorts the image badly.So if somebody is thinking of using something like this, be aware to really keep anything magnetic away. A mains transformer near this thing causes mayhem

author: weirdal1968
author_rank: Newbie
timestamp: May 10, 2014, 07:26:32 pm
content: Regarding the sensitivity of the CRT, I've never played with a lollypop CRT but I'm not surprised it is touchy. Since the vertical deflection yoke is scanning an angled/curved phosphor surface the normal sawtooth vertical deflection waveform is compressed and more easily distorted by external magnetism.