Dave's Clock - Page 1
Forum section: electronics / projects

author: neo
author_rank: Super Contributor
timestamp: September 09, 2016, 07:37:12 am
content: So i tried to get Dave's clock schematic accurate to pin numbers, did i do it right? or did i miss something and spend all that time banging my head against a wall doing this in error. Please anyone let me know if its right i already bought a vfd display for it. also the line of things under the vfds are transistors, the standard symbol wouldn't fit

author: EEVblog
author_rank: Unknown
timestamp: September 09, 2016, 07:50:42 am
content: I make no guarantees as to the accuracy of my schematic!

author: neo
author_rank: Super Contributor
timestamp: September 09, 2016, 07:56:02 am
content: and i especially make no guarantees to my replica im just asking if it looks right, hi dave big fan

author: neo
author_rank: Super Contributor
timestamp: September 09, 2016, 08:11:54 am
content: you will also note a little 555 timer circuit in that schematic that is my planned clock unless its a stupid idea i ran the numbers and with a 10 turn pot the accuracy seems fine.

author: obiwanjacobi
author_rank: Super Contributor
timestamp: September 09, 2016, 09:01:47 am
content: What does Q30 do?

author: neo
author_rank: Super Contributor
timestamp: September 09, 2016, 09:04:32 am
content: obi, thats part of the nor gate. by the way thanks you drew my attention to a missing wire in the schematic

author: void_error
author_rank: Frequent Contributor
timestamp: September 09, 2016, 11:42:22 am
content: The 555 wouldn't be good enough. The oscillation frequency will drift with temperature, depending on what timing components you'll use.Try aCD4060with a 32.768kHz crystal instead.And speaking of clocks, I almost want to design and build one just for fun.

author: neo
author_rank: Super Contributor
timestamp: September 09, 2016, 06:20:59 pm
content: void error, is 20 ppm good enough? and does the rest of it look fine?

author: neo
author_rank: Super Contributor
timestamp: September 10, 2016, 07:09:46 am
content: Well i got tired of trying to make sure dave's was right so i went and designed my own, perhaps taking note from other tries but largely my own. 20 ppm frequency drift on Y1

author: neo
author_rank: Super Contributor
timestamp: September 10, 2016, 07:16:17 am
content: What do you think of it?

author: neo
author_rank: Super Contributor
timestamp: September 10, 2016, 07:28:47 am
content: Quote from: wilfred on September 10, 2016, 07:21:24 amIn order, yes small typoyellow lines are for reference in drawing it only thanks for your concern on the printing of ittransistor arrays are drawn that way to save space their just regular MPSA42 transistors to power my vfd displaythe power supply itself is going to another page for simplicity's sake

author: neo
author_rank: Super Contributor
timestamp: September 10, 2016, 07:34:19 am
content: and in answer to a question not yet asked the z1 and z2 are the shortcut to the #6 reset circuit at the bottom again to save space and make schematic simpler

author: void_error
author_rank: Frequent Contributor
timestamp: September 10, 2016, 07:57:05 am
content: Quote from: neo on September 09, 2016, 06:20:59 pm20ppm means that your clock will be off by roughly +/- one minute every month, worst case.

author: VinzC
author_rank: Frequent Contributor
timestamp: September 10, 2016, 08:36:07 am
content: Might be too late but for a digital clock I'd recommend using mains as the clocking signal as the frequency is pretty stable.

author: void_error
author_rank: Frequent Contributor
timestamp: September 10, 2016, 08:59:22 am
content: Quote from: VinzC on September 10, 2016, 08:36:07 amThat's how a lot of those cheap mains-powered clocks do it. They also use a dedicated clock chip and some have a 9V backup battery that runs the clock without the power-hungry LED display when mains power is cut off, and usually run off an RC oscillator. I remember taking one of those clocks apart several years ago.

author: neo
author_rank: Super Contributor
timestamp: September 10, 2016, 04:59:37 pm
content: Quote from: VinzC on September 10, 2016, 08:36:07 amonly problem with that is im at the end of the line so its no better than a crystal, but thank you i did pursue that line of thought but i came up about even stability between the two

author: neo
author_rank: Super Contributor
timestamp: September 10, 2016, 06:20:06 pm
content: or at least with a crystal i have a known variable