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I am interested in learning more about the so-called "projection"
displays that were used in a lot of 1970s industrial rack-mount type
clocks.

Does anyone on here have a reference or source for them?

Thanks!

Mike Harpe
Sellersburg, IN USA

--
Please note my new email address:
mike@...

Here is a teardown







From: NEONIXIE-L@... [mailto:NEONIXIE-L@...] On
Behalf Of Mike Harpe
Sent: Wednesday, July 14, 2010 9:02 AM
To: neonixie-l@...
Subject: [NEONIXIE-L] "Projection" displays





I am interested in learning more about the so-called "projection"
displays that were used in a lot of 1970s industrial rack-mount type
clocks.

Does anyone on here have a reference or source for them?

Thanks!

Mike Harpe
Sellersburg, IN USA

--
Please note my new email address:
mike@... <mailto:mike%40mikeharpe.com>

the best way i have found to DRIVE the projection displays is a cd4028 decade counter decoder driver & 2x uln2003 transistors in 16 pin dip, it take's BCD code also a good trick is to drive the lamps at 12volts if thats what there design is? and use a 12vdc to 5 vdc voltage converter and run the logic on the 5 vdc and the lamps at 12vdc

Here is a page with pictures of a number of projection displays and other displays that use light bulbs. (A shameless plug warning applies, given that I made the page.)



Here is another page which shows several internal photos of a smaller projection display.



Richard Kline
www.decadecounter.com

--- In NEONIXIE-L@..., Mike Harpe <mike@...> wrote:

I am interested in learning more about the so-called "projection"
displays that were used in a lot of 1970s industrial rack-mount type
clocks.

Does anyone on here have a reference or source for them?

Thanks!

Mike Harpe
Sellersburg, IN USA

They're pretty simple devices. A matrix of miniature incandescent lamps illuminates text printed on photographic film and is focused onto a screen by a matrix of molded plastic lenses. If there was demand, it would be cheap to produce with modern injection molding but you would have to make a LOT of them before the price was reasonable. Unlike Nixie tubes, there is no esoteric equipment or "magical" formulas of materials and gas fill required.

--- In NEONIXIE-L@..., westdave <WESTDAVE@...> wrote:

the best way i have found to DRIVE the projection displays is a cd4028 decade counter decoder driver & 2x uln2003 transistors in 16 pin dip, it take's BCD code also a good trick is to drive the lamps at 12volts if thats what there design is? and use a 12vdc to 5 vdc voltage converter and run the logic on the 5 vdc and the lamps at 12vdc

Isn't there a 74xx series IC that is a BCD to 1-of-10 decoder with open collector outputs just for this sort of thing?

They can be multiplexed nicely too without side effects but you do have to put a diode in series with each lamp.

The lamp voltage varies, 5V, 12V, 28V, and likely others were available.