More electro-mechnical porn - Page 1
Forum section: electronics / general

author: rrinker
author_rank: Super Contributor
timestamp: February 29, 2016, 11:35:15 pm
content: Similar vintage to the B-52 piece Dave did a teardown on - slightly older.Same co-worker who had the old USN oscilloscope I posted in the Test Instruments section brought this bit in today.It's clearly a rotary encoder, you can see the three traces on the one side, with contacts, one is continuous, the other two are 90 degrees out of phase with each other. On the back side there is a spring loaded bracket with a little plastic bit that rubs on the wheel and switches contacts based on the direction of rotation. The wheel itself is about 5" in diameter and very heavy. There' what may be a part number on one side, DRA 34766, along with a date of 9-24-55 (coincidently close to my birthday, just 11 years too old). I tried googling variations of the part number, but no luck so far. He picked it up out of a box of surplus junk, so has no idea what it might have been part of. That flange leaves you to guess that it was installed in some sort of enclosure with the bulk of the wheel and the switches all inside and just part of the wheel sticking up.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: March 01, 2016, 03:43:34 am
content: Great. Now the Russians know all our secrets!

author: Brumby
author_rank: Unknown
timestamp: March 01, 2016, 04:20:06 am
content: Just looking at the 'encoding'.Each ring has contacts spaced 10º apart, with each ring offset by half this amount. The width of the contacts appears to be a quarter of this - an angular size of 2.5º - which would seem to be the same size as the spacing between inner and outer contacts.If we assign values of 1 and 2, we can get a series of state values:InnerOuterState000101000012000101000012This would indicate we could get a rate of angular change with a 2.5º resolution - but no reliable direction information, assuming the wheel will stop at some random point.That doesn't seem to me to be a particularly fine resolution for anything but rotary speed, yet it is using wiper contacts.Curious.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: March 01, 2016, 05:28:46 am
content: Quote from: Brumby on March 01, 2016, 04:20:06 amIt should be good enough for the typical turbo encabulator.

author: Brumby
author_rank: Unknown
timestamp: March 01, 2016, 06:16:09 am
content: That's true.The base plate does look like it could be prefamulated amulite - so you might be onto something.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: March 01, 2016, 06:35:02 am
content: It is a prefamulated amulite baseplate, but it's likely not suitable for measuring inverse unilateral phase detractor currents adequately. If you look at the reference GE unit specifications, it needs a drift under 3ft^2-hr/mo. Not going to happen without panandermic semi-boloid stator slots, which this unit doesn't have. I only saw those on the later prefamulated amulite baseplates. This unit was probably only good for use in parametric negative-time compensators.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 01, 2016, 02:01:20 pm
content: Ha ha. I can't top that.The scratches on one side show how far the wheel projected from the slot it must have stuck through. Took a fair bit of weight, but no sideways forces, judging by the bracket construction.Wonder why there are multiple scratches on one side, but none on the other?Might indicate it was right at the edge of a space in which something slid over it.

author: rrinker
author_rank: Super Contributor
timestamp: March 01, 2016, 02:13:11 pm
content: I think they were more like marks on it, not actual scratches in the metal. It's been nearly 24 hours since I had my hands on it and took the pics, but I don't think they were scratched into the metal at all..