If there is still any interest:
I just got the surplus plasma displays from Helmut Singer to work, with a bit of help and a example schematic from another forum. Looks beautiful and $$$, but i have no camera
.
The "scanning" is very similar to the Decatron (counting tube) principle. The cathodes are arranged in three (or 5 with other meters) groups like this:
[reset cathode][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3]
All with a common anode. You pull the reset cathode to ground potential and then go around repeating pulling the [1],[2],[3] cathodes to ground. After each switching the glow discharge will jump to the nearest grounded cathode, thus wandering to the right. This is done until the discharge has reached the last cathode. To control the length of the bar, the anode voltage is lowered after the needed number of pulses, switching the discharge of for the rest of the cycle. This allows connecting the cathodes of several displays in parallel and only switching the anodes.
All this is way easier than it looks, with a µC (i used a €2.75 AtMega8), 6 transistors, a few resistors and a 250V and 72V supply (just a few mA). The µC can be replaced with a bucketful of logic ICs, a DAC and a comparator per channel...
If there is interest, i can post a schematic and the µC program (when the latter is readable and AD is implemented )
If someone has a schematic for a log rectifier etc. without using $8 ICs, this could become interesting...
EDIT:
@Keith: I would be very interested in your documents, if you happen to find the time.
;Matthias
I just got the surplus plasma displays from Helmut Singer to work, with a bit of help and a example schematic from another forum. Looks beautiful and $$$, but i have no camera
.The "scanning" is very similar to the Decatron (counting tube) principle. The cathodes are arranged in three (or 5 with other meters) groups like this:
[reset cathode][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3][1][2][3]
All with a common anode. You pull the reset cathode to ground potential and then go around repeating pulling the [1],[2],[3] cathodes to ground. After each switching the glow discharge will jump to the nearest grounded cathode, thus wandering to the right. This is done until the discharge has reached the last cathode. To control the length of the bar, the anode voltage is lowered after the needed number of pulses, switching the discharge of for the rest of the cycle. This allows connecting the cathodes of several displays in parallel and only switching the anodes.
All this is way easier than it looks, with a µC (i used a €2.75 AtMega8), 6 transistors, a few resistors and a 250V and 72V supply (just a few mA). The µC can be replaced with a bucketful of logic ICs, a DAC and a comparator per channel...
If there is interest, i can post a schematic and the µC program (when the latter is readable and AD is implemented
)If someone has a schematic for a log rectifier etc. without using $8 ICs, this could become interesting...
EDIT:
@Keith: I would be very interested in your documents, if you happen to find the time.
;Matthias
