power supply for dg8f fluorescent tubes with mm5316 chip - Page 1
Forum section: electronics / projects

author: jim that guy
author_rank: Newbie
timestamp: March 21, 2023, 11:26:03 pm
content: I have a number of DG8F fluorescent tubes that I bought back in the 70s and never did anything with. I have a mm5316 clock chip that I would like to use. My problem is I would like to use possible 5v dc or even 12v but not sure how to get the 1.4 vac for filament power off same supply.Not wanting to use transformers.

author: floobydust
author_rank: Super Contributor
timestamp: March 22, 2023, 12:44:36 am
content: Welcome to the ForumsHey I remember those displaysFutabaISE Electronics Corp. (ISE DENSHI) iTRON DG8F from the late 1970's. There were bushels for sale at Radio shack and Poly-Paks surplus once somebody figured out making an 8-digit calculator with them is hairy. They are quite bright. Similar is DG10A.I have an old MM5316 alarm clock using GE Y-1938's which are electrically similar tubes.You need a power transformer to run a MM5316 because it requires 50/60Hz AC ref for counting. Unless you use a MM5369 or the equivalent made with aPIC 12C508.What I did is power the clock from a mains-12.6VAC transformer making around 17VDC for power, then I put another small 115V-12.6VAC connected to the first transformer's output get the 1.5VAC. You could also wrap a couple turns around the main power transformer core to make a filament power winding.Otherwise, if you run the filaments in series from DC, you get a (cathode) voltage gradient across the display which shows up as one end being brighter than the other.The filament voltages could be 0V-1.4V, 1.4-2.8V, 2.8-4.2V, 4.2V-5.6V which would be a lot dimmer.To lessen that, you could power from a separate (isolated) DC supply and ground the filament string midpoint to the clock chip power GND - that gives only ~2.8V difference.You would add an inrush resistor as well for the string.A modern IC for VFD filament driving is the obsolete LM9022 which gets rid of the transformers.Some people seem to use an audio amp chip like LM4871 to accomplish the same thing.edit: Old Noritake info on DC and AC power of VFD filaments:https://www.noritake-elec.com/technology/general-technical-information/vfd-operation

author: rdl
author_rank: Super Contributor
timestamp: March 22, 2023, 02:09:34 am
content: Those data sheets attached all show VAC/DC for the filament voltage. Doesn't that mean either would work?

author: w9gb
author_rank: Contributor
timestamp: March 24, 2023, 11:09:27 pm
content: Do NOT Apply “Too Much” Voltage to the VFD.Heathkit GC-1107 Clock used VFD … here is schematic.https://www.nostalgickitscentral.com/heath/schematics/heathkit_schema_gc1107.pdfYou can Read and Examine the Heathkit Clock, that used that MOSTEK Clock Chip with a VFD. Power Supply and Cntrols on Schematic diagram, and List of Parts.Heath GC-1107 MANUALhttp://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_G/gc-1107/gc1107_man.pdfHeath used Mostek Clock ICs in 1970s and early 1980s.http://www.decodesystems.com/vfdclock.htmlDIY Build using MM5316N clock chiphttps://en.kohacraft.com/archives/making-a-clock-using-vfd-display-tube-iv-6-and-mm5316n.html