TSOP as a proximity sensor?

A few days ago, a friend came over to talk about some microcontroller related projects. One of the topics was distance sensing, or rather proximity/movement sensing with low technical effort.

The basic idea was to detect movement of an object or person within a short distance to trigger events. Typical sensors for this kind of application would be passive infrared (PIR) modules, radiowave sensors (microwave or radar) or active infrared distance sensors. All of these can be quite pricey, perhaps with the exception of the PIR, which cannot detect objects very well.

So, I thought about how the goal could be accomplished with standard parts. Active infrared is the most simple choice. [Read More]

PBG12201 plasma displays

Bar display with reservoir cap in HV circuit

I picked up some unusual plasma displays from ebay some weeks ago, which I have been searching for quite some time now. The picture above shows an illuminated Burroughs PBG-12201 plasma bargraph display. They are pretty hard to get by now, and if available, prices are a real shocker. Some shops in the US that carry them ask for 230 USD and some even more. Sometimes they appear on ebay for about 50 USD, but you have to be real quick to get some. Best chances are with surplus stores that sell off leftover production stocks or disassembled devices that originally contained such tubes. A few very retro and very popular mixing consoles for audio applications used them as main VU meters (eg. made by Lexicon),  as well as some current professional grade standalone meters (eg. RTW, one of those is where I first saw such a display and was absolutely fascinated by the deep orange hue). As they eventually get old and start flickering or burning in if not properly cared for, spare parts have become rare, and since Vishay – the most recent producer of these displays – has discontinued the product line in early 2012, I would expect the market to dry up even more.

Mine were obviously scavenged from some kind of device by a Hungarian ebay seller, he offered some 10+ pieces of the PBG-12201 type display for 8 Euros each – a real steal! I just couldn’t resist and got myself three of them, together with matching sockets. Thinking back, I don’t get why I ordered three instead of four…oh well, it’s done. The tubes show some signs of wear, like glass chipped off around the edges and burn marks on the cathode traces, but they all work fine. [Read More]

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