Daves clock, from russia with glow version - Page 1
Forum section: electronics / projects

author: neo
author_rank: Super Contributor
timestamp: October 12, 2016, 08:05:11 am
content: This is going up early due to request, the first half isnt documented but i will do my best from here on out.There are two more vfds to go on the top, seconds and an am pm indicator, everything is 4000 series, the oldest actually being from 1970, this clock in my mind has a bit of a 1969 theme and i should note that i did not come up with "from russia with glow" and it has a few tweaks from Dave's design, the chip list, 8 4026 , 2 4012, 1 4069, 2 4013b, 1 4060, and 1 4027.

author: neo
author_rank: Super Contributor
timestamp: October 12, 2016, 08:10:33 am
content: one more picture, this one of the board

author: neo
author_rank: Super Contributor
timestamp: October 12, 2016, 09:39:18 am
content: one important point, these light up fine at 5 volts so their similar to leds only with a couple more connections, also what do you recommend looking up on ebay for a filter? anything cheaper than plexiglass? will plexiglass even work (opaque of course)?

author: Ian.M
author_rank: Super Contributor
timestamp: October 12, 2016, 10:01:28 am
content: Opaque Acrylic sheet (e.g. Plexiglass, Perspex or various other brand names) wont work. It needs to be translucent and fairly high colour density. The alternatives to Acrylic are mostly a P.I.T.A to work with or have inferior properties. One possibility would be clear sheet backed by a filter gel. If the edges of the plastic sheet are to be concealed by a frame, that could work quite well.Have you got a link to Dave's original design? I found your old thread about it:https://www.eevblog.com/forum/projects/dave%27s-clock/but that didn't link the original.

author: neo
author_rank: Super Contributor
timestamp: October 12, 2016, 11:15:16 am
content: http://www.eevblog.com/files/DigitalClockSchematic.pdfhttps://www.eevblog.com/forum/blog/eevblog-801-how-to-design-a-digital-clock/as for that filter i now feel like an idiot i didnt even think of the word translucent, not only with it work it cheaper than opaque, thanks

author: Pjotr
author_rank: Frequent Contributor
timestamp: October 12, 2016, 11:26:07 am
content: What works pretty well with VFD's are circular polarising filters. Polaroid HNCP-37 was specially made for electronic displays. Although Polaroid doesn't exist any more, Google for a second source. Those filters block any reflected light from metal and glass and work also great with Nixies. However they don't work with plastics (LED 7-segment), because plastics randomise the polarisation again..

author: neo
author_rank: Super Contributor
timestamp: October 12, 2016, 11:48:37 am
content: Thank you Pjotr that is an excellent idea and i may use it in the future though for this particular project 140 (us)dollar filter is a bit much despite how much i like the way it looks

author: Pjotr
author_rank: Frequent Contributor
timestamp: October 12, 2016, 12:05:03 pm
content: If you Google around you will find them for less than 1/10. Problem is to find a supplier that delivers small sizes/quantaties.

author: neo
author_rank: Super Contributor
timestamp: October 12, 2016, 01:56:00 pm
content: the display is done

author: neo
author_rank: Super Contributor
timestamp: October 12, 2016, 02:08:43 pm
content: Quote from: Pjotr on October 12, 2016, 12:05:03 pmmy problem is i dont need a small piece i need half a square foot

author: Pjotr
author_rank: Frequent Contributor
timestamp: October 12, 2016, 02:52:43 pm
content: Are you planning that big VFD'sYou can have a look at a supplier for theatre lighting. Those have usually a big assortment of polyester colour lightning filter sheets, or even rolls. You can attach those filters durable without air bubbles to 3mm (0.12") thick acrylate with 3M 468MP glue sheet.

author: neo
author_rank: Super Contributor
timestamp: October 12, 2016, 11:34:02 pm
content: The seconds are really dim their filaments got a very brief less than 2 second pulse of 12volts while i was mapping the wires, the main board got a couple more accidents than that and it still works (perhaps just more to cushion the shock), did i kill the seconds part? or maybe i could put more volts in them as a solution?

author: Ian.M
author_rank: Super Contributor
timestamp: October 13, 2016, 12:05:59 am
content: Its possible to damage the high emission coating on the filament if its run at elevated temperature without anode current. Normally that takes a fairly long time to happen. Are you 100% certain the tubes are bad? Stop the clock and compare voltages with another fully working digit with the same number of lit segments.

author: neo
author_rank: Super Contributor
timestamp: October 13, 2016, 12:49:24 am
content: i dont know why but the seconds broke all the rest are fine and its only a failure rate of 22% which given that this is perfboard by a beginner is pretty amazing in my opinion, and i dont have the clock up and running thats next i just had the display done but now i have to redo a portion of it, luckily i have a spare tube so i can take the am/pm indicitator and use it as a seconds tubes, im going to use a ne-2 neon bulb for the am pm indication now

author: DaJMasta
author_rank: Super Contributor
timestamp: October 13, 2016, 02:08:49 am
content: Looks neat, but what kind of tubes are those? LEDs inside of glass bubbles?Normal nixies require a pretty high voltage drive, so you'd need specialized interface circuitry to be able to switch them without blowing out your chips - but if they're LEDs, then barring a whole bunch of current through either side, they should be quite durable and would last a very long time.Also I don't think socketing the capacitors is required

author: neo
author_rank: Super Contributor
timestamp: October 13, 2016, 04:18:51 am
content: IV-6 vacuum fluorescent displays also the dots are iv-25, and the part of the board where you see socketed capacitors is the crystal part (no crystal yet) so yes socketing is useful, but not required, i can put in a bunch of different caps easily until i get a couple of good ones

author: neo
author_rank: Super Contributor
timestamp: October 13, 2016, 11:43:12 pm
content: i redid the display i accidentally broke the pins on two iv-6 tubes (too many tries to get them right), they can easily be fixed with conductive epoxy i think, for now i have a 5 volt bulb (think minature light bulb) displaying the am/pm indication, also i finished the power supply (more pictures later) and all i have left is the main board, it going to get difficult trying to find 60 or 70 different colored wires but i think ill manage

author: neo
author_rank: Super Contributor
timestamp: October 14, 2016, 10:16:05 am
content: more pictures, also this is probably the last time those chips will see light their fixing to be smothered in cables, since you cant read the metal can text, its a lm309 with a lm317 on the inside for the filaments, that case is two things a heatsink and ground, thats a 13 volt power supply regulated to 5 and then to 1.5 volt or so. The filament voltage comes out of the 317 and is then dropped by two diodes (one for each filament type) i chose to do it this way because it provides a bit of safe margin. Also on a side note the man who owned that shed full of parts before me (he is now dead, auctions are nice) must of liked the lm309 he bought hundred at least 20 years ago and only has a few leftEDIT: to anyone who noticed that the ground wires were on wrong, great observation skills, since fixed however

author: neo
author_rank: Super Contributor
timestamp: October 15, 2016, 11:11:29 pm
content: ok don't ask me why but the biggest part of my display wont light up, i took the tubes off and even indirectly they would not light up (well unless i massively overvolt them) so this project temporarily is on ice while i wait for more to show up, to confirm 4 iv-6 tubes are bad perhaps they were when i got them i dont knowand as a post note im going to hand draw a circuit board for the new tubes assuming i can

author: Ian.M
author_rank: Super Contributor
timestamp: October 16, 2016, 01:27:52 am
content: Sorry to hear that. If you've bent the leads too much too close to the seals, its possible you've lost vacuum which would account for your tube failures. The silvery or iridescent getter patch in each affected tube will loose its sheen and go whitish within a few days if you have lost vacuum.When you do the rebuild I'd personally make it modular with a sub-board for each IV-6 so you can easily swap tubes around and you don't ever have to rework them because of the fragility of their leadout wires. The alternative is to machine or 3d print plastic bases for them that support the wires to prevent them being bent where they come through the seal so you can desolder/resolder them fairly safely. (WITHOUT BENDING THE LEADS OVER!)Are you going back to the planar 6 digit VFD + Arduino clock project while you wait for parts for the 'trad' Russian one?

author: neo
author_rank: Super Contributor
timestamp: October 16, 2016, 01:54:37 am
content: yes i will and good news my etching experiment was a success (well relatively but it worked in the end albeit slow) also the reason why im making my own circuit board for them if perfboard is square, with tubes its an old analogy square hole round peg it can fit but not elegantly so im attempting to make a pcb with the right hole pattern. Ultimately i consider the failure as a lesson.post note, the ones i bought are a new old stock set where as these were used perhaps new will be more forgiving (that is not to say i will be as careless)

author: neo
author_rank: Super Contributor
timestamp: October 28, 2016, 03:09:27 pm
content: Good news, the new tubes have arrived from russia and im going to start up again and soon, the first tubes did not die in vain i won a cd as a (indirect) result, i sat there working on the display with the radio on for hours on end and as a result of that i won a cd, changesonebowie

author: Ian.M
author_rank: Super Contributor
timestamp: October 28, 2016, 03:23:17 pm
content: Treat them like precious babies, and make sure they are supported with no mechanical stress on the lead/glass seal (i.e. don't bend it anywhere near the seal and put a cut to shape piece of foam tape between the tube base and the board so its got cushioning to allow for thermal expansion) and your luck should be a lot better. Be careful not to over-voltage the heaters again - if your design makes it easy to short to +12V, redesign it to make it safer!Take another look at the failed tunes - if you can see a change in the getter spot compared to the N.O.S. ones, they lost vacuum due to cracked seals.

author: neo
author_rank: Super Contributor
timestamp: October 28, 2016, 03:29:46 pm
content: i wholly intend to treat them like babies, last time it took me a half hour a tube this time ill probably take an hour or more, but besides that heres one important consideration these are new so i have more lead length and wont be forced to try and force something toxic, and as for the filaments before i had them in one big lot of wires this time i think im going to use cat-5 (old cable that i can cut up) to bring them off in their own bundle, and then theres the fact that this time around im paranoid and will check everything 10 times before voltage is aplied

author: Ian.M
author_rank: Super Contributor
timestamp: October 28, 2016, 04:47:32 pm
content: The price of the tubes being what they are, its worth cutting up a GOOD NEW CAT 5 patchlead for hookup wire. Colour coding is good - so you know which are the filament wires, grid and anodes at a glance. Even on breadboard, I try to keep consistent colour coding. e.g fromreply #133of your old thread,you can see I've used white striped with green for all the high voltage tube drive lines, white with grey for the logic level parallel data out of the shift registers, grey striped with white for the serial data from Arduino MOSI, orange for +5V and brown for 0V supplies, and white striped with orange and with brown for logic pullups/pulldowns to 5V and 0V respectively. If I'd had red and black wire I wouldn't have used orange and brown, and there's a green striped with white wire grounding the breadboard baseplate, which isn't consistent with the use of brown for the rest of the 0V rail. I didn't have to worry about a colour for the HT rail as the +30V rail is on a bus strip (just above the transistors) and only has component leads connected to it.I don't use colour coding for the bit order of similar signals - if I miscount it wont let the holy smoke out. However if I mix up power and data or connect a signal with 30V levels to a 5V chip, my board will definitely elect a pope!Jumper kits colour coded by length are the invention of the Devil and promoted by his chief minions!

author: neo
author_rank: Super Contributor
timestamp: October 28, 2016, 08:17:56 pm
content: when i say old cat 5 i mean 3 wire cable that is either telephone or internet that is physically fine as wire but is missing an end so im free to cut it up, i figured it out while waiting that it would be the perfect one to use for the filament and the grid. and last time i tried color coding and it worked so what i do now is going to be a better version of that.

author: neo
author_rank: Super Contributor
timestamp: October 28, 2016, 08:29:21 pm
content: one problem with the filaments is the iv 6 filaments want .8 volts the the iv-25 want 2.25 volts though ive been reading on old filaments that they could be wired in series to increase voltage so unless you object im going to (carefully) experiment with that, also i never did ask but what do you think of the iv-25 tubes as the colon mark, unlike tradition i plan to use 3 dots for each colon

author: neo
author_rank: Super Contributor
timestamp: October 31, 2016, 03:34:58 am
content: new display layout complete

author: Ian.M
author_rank: Super Contributor
timestamp: October 31, 2016, 09:33:09 am
content: There are several problems with series filament connection.First and most important, it introduces a brightness variation between digits due to the differing cathode voltage and thus Vak. the effective HT 'seen' by each tube. Even with my little 4 digit planar VFD, the variation in brightness between digits caused by 1.7V DC filament drive with 25V HT is noticeable at very low brightness levels.Secondly there will always be some statistical variation between tubes and if voltage-driven it over-stresses the thinnest and weakest filament at power-on - being thinner it both has more resistance and heats up quicker, so has a greater share of the voltage until the other filaments come up to temperature. You've already seen the problems 2 seconds of filament overvoltage can cause, so why subject your new tubes to extra stress for a tenth of a second every powerup? Historically, series filaments were always a cheap hack used in equipment where the manufacturer wanted to avoid the cost of a filament transformer. If your clock is AC powered, the best option is a 3V transformer + a dropper resistor in series with each filament. Otherwise run them in parallel from a low voltage rail. Remember, a small negative bias is needed to get a good clean cutoff so if using DC filament drive, there are advantages to hanging the filaments off the 5V rail and putting the dropper resistors between them and ground. To ease power-up stress due to the thickest filament hogging the current or if one should ever blow, each should have its own dropper resistor. If you need something more efficient, look at negative output switching regulators with a buck topology, run between +5V and Gnd to provide a +2.75V rail that is 2.25V below the +5 rail and can sink the total filament current.

author: neo
author_rank: Super Contributor
timestamp: October 31, 2016, 02:50:56 pm
content: so ill just go back to my original plan, run the dots off an lm317 and tap into the reference voltage and drop it with a diode, which i tested and found to work

author: neo
author_rank: Super Contributor
timestamp: November 03, 2016, 05:06:01 am
content: to all those wondering why there are no updates on this project, my chinese crystal apparently dont work seeing as how i got nothing from it and so it took me a bit to figure out how to obtain pulsating dc from ac.