Building relay clocks - the project promotion - Page 1
Forum section: electronics / general

author: Spemo
author_rank: Regular Contributor
timestamp: September 20, 2019, 02:32:44 pm
content: Hello everyone,about a year ago I built my first relay clock based on my own schematic, with decimal counters, loads of diodes and wires.Here is a thread about the story of all of it, if you want to know more:https://www.eevblog.com/forum/projects/the-(long)-story-of-the-relay-clock/new/#newSadly, I've run out of money now, and I got fed up with handwireing everything.I spent about a month on KiCad, trying to find the right design, simplify it a bit and pretty much translating everything from my picturial diagram into KiCad.I ended up with the simplest way of this clock which is a 12 hours design, no fancy gimmics like automatic brightness dimming or something like that.So here is the link to GoFundMe:https://www.gofundme.com/f/building-relay-clocksIf you're interested in sponsoring this project, or decide to do so, I'd greatly apreciate it. Sharing the GoFundMe page on facebook, twitter or something like that would help out too!If you want, I'll put your name on the PCBs as a sponsor.The minimum order quantity for PCBs is 5, and I don't need 5 clocks.... So my plan is to either give one or two to the biggest contributors, or sell them, or whatever.If you have an idea, please share it with me.A side note: the PCBs themselves are not that expensive, around 40€ delivered, but all the parts and necessary tools add up to the goal I set.I you want to have one when everything is done and built, feel free to contact me.Have a nice dayDaniel

author: mariush
author_rank: Super Contributor
timestamp: September 20, 2019, 04:05:42 pm
content: Have you tried optimizing the circuit first and reducing component count?For ex.See if you can replace 7 npn+base resistors with something like ULN2003A :https://lcsc.com/product-detail/Darlington-transistor-array-driver_Unisonic-Tech-ULN2003G-S16-R_C73286.html7 cents each for 7 darlington transistors, built in resistors for base of transistor, diodes for relay protection etcOr replace individual diodes with common cathode diode packs ... ex BAV70 for 0.7 cents each in volume :https://lcsc.com/product-detail/Switching-Diode_ON-Semicon_BAV70LT1G_ON-Semicon-ON-BAV70LT1G_C82479.htmlYou can interleave those 3 pin diodes to take less space and make groups of 4 to reuse them (if you want to) ex... :^ you'd have one 0.1" hole right where the vscore would be, so if a 8 diode pack would have 11 pins (one unused in middle)optionally you could add a jumper link at the opposite side so to join the two cathodes together on the circuit board instead of through the header.Or you could make your circuit board double sided, with 2 of these on each side for even more shrinking but it would be more time consuming to solder all parts. Basically you'd have to apply paste with stencil or manually tin pads, place parts on side, use hot air to solder side, flip board, apply stencil, paste, parts, hot air the parts on second side.Even with plain diodes, it would be faster for you to use surface mount parts ... ex 0.4 cents each for 4148 :https://lcsc.com/product-detail/Switching-Diode_IN4148W_C181134.htmlhttps://lcsc.com/product-detail/Switching-Diode_Shandong-Jingdao-Microelectronics-1N4148W_C115103.htmlAlso, maybe you don't need an expensive and voluminous 220uF electrolytic, maybe a couple ceramic capacitors in parallel would be plentyfor example 1..2 x 0805 22uF 25v caps may be enough :https://lcsc.com/product-detail/Multilayer-Ceramic-Capacitors-MLCC-SMD-SMT_SAMSUNG_CL21A226MAQNNNE_22uF-226-20-25V_C45783.htmltantalum capacitors may also be an option, at 10 cents each for 47 or 100uF.. here's some examples:https://lcsc.com/product-detail/Tantalum-Capacitors_AVX_TAJA476K006RNJ_47uF-476-10-6-3V_C7190.htmlhttps://lcsc.com/product-detail/Tantalum-Capacitors_AVX_TAJB107M010RNJ_100uF-107-20-10V_C7196.html

author: Spemo
author_rank: Regular Contributor
timestamp: September 20, 2019, 04:44:02 pm
content: Quote from: mariush on September 20, 2019, 04:05:42 pmYes, I have tried optimizing everything, and this is the lowest part count with dedicated parts. I have looked into using parts that combine multiple things into one package. As for the transistor arrays: I'd be giving away space with lots of DIP-16 parts, and as for SMD components: I am not capable of soldering SMD parts, my hands are too shaky for that.Sure, there are more individual components, but this way it is as tightly packed as it gets, and the relay protection diode will be soldered on the other side of the board (so kind of double sided).As for the capacitors:I have tried reducing the capacitance, but with the limited resources I had ( NPN transistors, relays, resistors, different value capacitors), 220µF is the lowest I can go for the delay needed (the bottom relay needs to turn on a bit later than the top one in the row, which is done with a resistor charging up the capacitor). Sure, lower values equal less space used, but I can't find a solution for this.putting 784 components together sure is a lot of work, but also a challenge in my mind....here's the basic schematic for the counter modules:Thank you for your input

author: mariush
author_rank: Super Contributor
timestamp: September 20, 2019, 05:02:43 pm
content: also you posted some prices in the other thread:QuoteThose are big prices... already gave some examples.Even the relays can be bought cheaper or almost same price but new, here's an example:https://www.tme.eu/en/details/leg-1a-5/miniature-electromagnetic-relays/rayex-electronics/leg1a-5/23 euro cents + vat if you get 250 of them. It's either cheaper or about the same price. Downside is they're a big bigger.Capacitors can cost as low as 1 euro cents (+vat) each if you buy in volume, here's example:47uF 25v:https://www.tme.eu/en/details/ce-47_25pht-y/105degc-tht-electrolytic-capacitors/aishi/100uF 16v:https://www.tme.eu/en/details/ce-100_16pht-y/105degc-tht-electrolytic-capacitors/aishi/and you can probably buy 1000 resistors for 3 euro... and 7 euro for timing circuit? please...You'll probably also get better circuit board prices if you make a more standardized size.Or, for example, take advantage of theirspecial offer of 2$ for 100x100mm boards.You say your board is 282x356mm ... redesign it to 300 x 300 mm ,,, that gets you 9 x 100x100 panels times 5, or 18/5 = <4$ per board. They make 10 100x100 for 5$ ... so that would take your price down to 9x5 /10 = 4.5$ per 300x300 boardEven if you redesign it to 300 x 400, you're still looking at 12 x 100mm squares , or 24$ / 5 = < 5$ per circuit board.Do a few hours of research and get better prices.

author: Spemo
author_rank: Regular Contributor
timestamp: September 20, 2019, 05:28:31 pm
content: Quote from: mariush on September 20, 2019, 05:02:43 pmThe prices for this complete thing (5 complete clocks) are as follows:33€ for the PCBs including shipping (JLCPCB)6,30€ for all the 600 LEDs1,32 for 400 1KOhm resistors0,17€ for 50 180Ohm resistors0,17€ for 50 10Kohm resistors1,10€ for 100 6,8MOhm resistors (ebay)0,15€ for 50 330K Ohm resistors1,50€ for 5 crystals (local)2,30€ for 20 33pf disc capacitors (local)1,75€ for 5 CD4060BE (local)2,25€ for 5 CD4027BE (local)2,94€ for 300 2N2222 NPN transistors2,20€ for 250 220µF electrolytic capacitors162€ for 500 DPDT 5V relays (0,29€ per relay)6,84€ for 1900 1N4148 Diodes5€ for 5 Micro USB step up convertersshipping 12€Total price for all 5 clocks:240,99 (excluding import tax)material price per clock: 48,20All parts ordered from LCSC, except the 6,8Mohm, the local stuff, and the dc-dc converters.Have a nice dayDaniel

author: mariush
author_rank: Super Contributor
timestamp: September 20, 2019, 05:40:24 pm
content: QuoteYou can place the ULN2003A chips vertically, on small boards... either prototyping boards or custom made boards.You conveniently have all the base pins on one side of the DIP package, and the COM pins on the other side, so you could have a single 2x8 header that replaces 7 transistor footprints and resistors and relay protection diodes:Also, if you put such a daughterboard by a group of 7 relays, you can probably route the traces on that board in an easy way, right under the relaysYou can do the same for your resistors. Instead of having them flat and use space, make small daughterboards and have 2x whatever pins you need:example stripboard (continuous strips) :https://www.ebay.com/itm/DIY-solder-2Pcs-stripboard-veroboard-uncut-PCB-Platine-Single-Side-Circuit-Board/401888922269

author: Spemo
author_rank: Regular Contributor
timestamp: September 20, 2019, 07:44:20 pm
content: Okay,your idea makes sense to me. All the capacitors still have to go somewhere though, so I don't think I'd save much space, and those daughterboards have to be soldered aswell....Here's a picture of one of the PCBs, red lines are front copper, green are backside, blue is front silkscreen violet backside silkscreen. That also represents where the parts are.the capacitors are 5mm in diameter, diodes for the relays on the backside.The only things which consume a lot of space are the diodes, which convert the decimal to 7-segment. They are on the Displayboard, the size for that is fixed, the other counter boards will go on the backside, kind of like this:The displayboard has to stay flat, so I found this (apart from all those diodes which have to be soldered) the nicest way, without going SMD.So this complete board will be cut into 4 seperate parts.Sure, I could squeeze everything onto those small 100x100 boards, but the complexity with this increases a lot, and in my opinion won't look that nice,have a nice dayDaniel

author: mariush
author_rank: Super Contributor
timestamp: September 20, 2019, 09:06:02 pm
content: I wanted to ask, out of conversation flow: what's the reason for those 5v boost (step-up) regulators you mentioned?You said "5€ for 5 Micro USB step up converters" in a previous comment.As you have so many relays each consuming 50-100mA while active, I suppose you use a decent amount of power while idle. Wouldn't it make more sense to use a 9v..12v adapter and use 5v dc-dc converters to provide power closer to the relays instead of going with voltage through the circuit board all over the place?Also seems you have 4 leds per segment, so maybe those can be driven directly from 12v (with a single resistor to limit current for the segment)There's cheap dc-dc converters ready made, likethis for example, which can provide up to 5A of current on 5vback to being on topic or reply to previous message...It's quite difficult for me to follow those schematics or even understand what's going on.As for diodes, another option you can have is to mount the diodes vertically, like so, but from the back of the board:See pictures in this thread as well (and the answers are informative):https://electronics.stackexchange.com/questions/101896/what-reasons-are-there-to-avoid-vertical-through-hole-resistorsYou can basically make a custom footprint for the diodes which is two through holes, 0.1" apart like a pin header, and just rearrange them to be more compact... you know the square shape is cathode, the other is anode.. so no need for silkscreen... or you can simply make a square with a bar on the square hole side.I'd like to mess around with the layout when i have some spare time, if you're willing to share the design. Maybe i can come up with some better layout (if you're interested in further reducing the board size). It's not like I'm gonna go in business selling such clocks so there's no risk to you if you share it.

author: Spemo
author_rank: Regular Contributor
timestamp: September 21, 2019, 06:23:53 am
content: The reason for the 5V step up regulators is that the whole circuit is running at 5.6V, because I have to account for the voltage drop of some of the diodes used. atleast in previos versions, this voltage was the most reliable. Sure, I can use DC-DC step down converters, but my goal here is to make it run off standard USB cables and chargers, which usually are able provide this kind of power.The Idle current is about 1A at 5.6V. With this "reduced" version I believe it will be a bit lower (less relays active at the same time).Every relay consumes about 50mA while active (they are rated at 40 I think)as for the display LEDs: the problem is that it is cursive. Would be like a regular 7-segment, then It would be possible to run them at 12v directly, but in this case, for example it it displays 1, there is a gap inbetween the segments, which I like to have illuminated. Like this:to get it to look like this, some LEDs ave two inputs, to either turn on with one segment or wit the other.Oh, and I forgot, the output voltage of the counter modules is also 5V.For the diodes: o thecoutner modules, there is enough space on the backside to mount them in flat, and on the display module, there is enough space for that aswell.the resistors between the relays are mounted vertically.for me, the only reasonable place to get component count down is on the display, with dip-16 diode packages or something like that. On the counter modules- there is not much to do, since the relays take up 90% of the space.Have a nice dayDaniel

author: ebastler
author_rank: Super Contributor
timestamp: September 22, 2019, 06:16:14 pm
content: Quote from: Spemo on September 21, 2019, 06:23:53 amThat seems unnecessarily complex. Why can't you arrange the vertical segments to form continuous vertical lines on either side (or slanted lines, if you prefer that appearance), then arrange somewhat shorter horizontal segments inbetween? I can't see any numeral where that would look wrong. Then each of the seven segments could be simply driven by one control signal, with the LEDs in series and/or in parallel as you prefer.The drawing below does show gaps inbetween the two segments forming one vertical line, but you could easily space all LEDs in that line equidistantly to avoid that.

author: Spemo
author_rank: Regular Contributor
timestamp: September 23, 2019, 06:21:21 am
content: Quote from: ebastler on September 22, 2019, 06:16:14 pmYou're right - I completely missed this way of arranging it. It's not cursive then, but still looks good to me.Thank you for your input!Have a nice dayDaniel

author: ebastler
author_rank: Super Contributor
timestamp: September 23, 2019, 06:32:19 am
content: Quote from: Spemo on September 23, 2019, 06:21:21 amThanks! You could tilt/slant the whole arrangement a bit more, to get a cursive look, and it should still work in the same way?Best of luck with your next generation of relay clocks! Would you mind posting a link, or the seller name or type number, for those low-cost DPDT relays? I have been dabbling with ideas for a relay computer, and the relays are obviously a big cost factor... (Have you already tried the ones you picked from AliExpress?)Thanks,Juergen

author: mariush
author_rank: Super Contributor
timestamp: September 23, 2019, 09:16:07 am
content: tme.eu has reasonably cheap dpdt relays that are new5v 0.56$ + vat for 1000pcs :https://www.tme.eu/en/details/lm2-24d/miniature-electromagnetic-relays/rayex-electronics/12vThe company (Rayex) has website and everything, with an "add to basket" feature that goes to an "inquire" button :https://www.relay-rayex.com/RS-SERIES-pd6936565.html... if you plan to order a few hundred maybe they'd be willing to sell directly at potentially cheaper price.

author: Spemo
author_rank: Regular Contributor
timestamp: September 23, 2019, 09:47:57 am
content: Quote from: ebastler on September 23, 2019, 06:32:19 amI found really cheap ones on LCSC. The one I planned to use was this one:https://lcsc.com/product-detail/Relays_HFD27-005-S_C23911.html0,30€ each if you need more than 100. Also, you can enter HK19 DPDT relay into the ebay search, but keep in mind they are used relays. But there you can get them at 0,25€ each.Have a nice day

author: ebastler
author_rank: Super Contributor
timestamp: September 23, 2019, 10:41:55 am
content: Quote from: mariush on September 23, 2019, 09:16:07 amThanks Mariush! I had looked at TME back when I started to dig into relay computers. I have ordered other parts from them several times, always very smooth. Annoyingly, the 12V version of the same relay (which I had assumed I'd use) costs about twice as much... But 24V should work as well: It limits the selection of power supplies a bit, but the lower currents on the PCB can't hurt!

author: ebastler
author_rank: Super Contributor
timestamp: September 23, 2019, 10:49:27 am
content: Quote from: Spemo on September 23, 2019, 09:47:57 amThank you! That's a good price indeed for new DPDTs.Have you used the 5V coil voltage in your prior clock designs, and did it work well for you? I would be a bit concerned that diode voltage drops are no longer negligible, if you have multiple diodes in series with a coil.(Not sure what one would really end up with in clock or computer logic -- it's probably quite feasible to limit the depth to two diodes in series? Ideally I would prefer to build entirely without logic diodes, since solid-state diodes were not available when e.g. Zuse built his relay computer. But that really drives the relay count up...)

author: mariush
author_rank: Super Contributor
timestamp: September 23, 2019, 11:45:38 am
content: Quote from: ebastler on September 23, 2019, 10:41:55 amI linked to the 24v by accident... they were the cheapest at 0.39$+vat for 500pcs but not stocked.Here's the 12v :https://www.tme.eu/en/details/rs-5-l/miniature-electromagnetic-relays/rayex-electronics/and here's the 5v :https://www.tme.eu/en/details/rs-5-l/miniature-electromagnetic-relays/rayex-electronics/

author: Spemo
author_rank: Regular Contributor
timestamp: September 23, 2019, 08:06:37 pm
content: Quote from: ebastler on September 23, 2019, 10:49:27 amYes, I have always used the 5V variant, since they were the cheapest to get on ebay. They reliably close at around 3.5 to 3.7V, and the input voltage to the clock itself is set to 5.6V, to eliminate any problems with diode voltage drops. If I remember correctly, there is always only one diode in series with a relay. Only the outputs have 2 diodes in series, one to change decimal to 7 segment, and at the 7segment for the cursive effect.And yes - not using any silicon in such projects drives the relay count up dramatically - in this case (with the clock) it would most likely double it again - imagine mounting 200 relays on a single PCB, just to get a clock..... and the power consumption

author: mariush
author_rank: Super Contributor
timestamp: September 23, 2019, 08:25:18 pm
content: Maybe in a future project you'd use solenoid to slide a board or turn a rotating wheel (like multimeters) to turn on/off all seven segments of a digit at same timeImagine a ruler like board that's pushed by a solenoid and you have pads on the board and short contacts/needles/springy bits that press on the board from above thus turning on or off segments. If there's a pad, two needles / pins from above touch the same pad, you get connection and segment lights up.Or have infrared leds on bottom, sensors on top and an opaque board with holes in it for where you want segments to light up or not, like old punch card ... light goes through, infrared beam hits detector and segment is turned on.I figure it would be harder to precisely stop exactly where you want (unless you go with stepper motor and stepper motor driver per digit) and you'd also have to implement return to 0 to set the new value every time digit changes.I guess a "reset signal" could be sent every time any digit needs to change to pull back the solenoid to 0 and have the set digit with a delay, something like 20-50ms later set digit.

author: ebastler
author_rank: Super Contributor
timestamp: September 23, 2019, 08:40:46 pm
content: Quote from: mariush on September 23, 2019, 08:25:18 pmIf mechanisms are allowed, you might as well build something like this -- probably with hardly any relays at all:

author: FreddieChopin
author_rank: Regular Contributor
timestamp: September 23, 2019, 08:46:12 pm
content: Quote from: ebastler on September 23, 2019, 08:40:46 pmThat thing looks like a shaver, maybe you could even hack a shaving mechanizm here so you can shave while you clock something.

author: Spemo
author_rank: Regular Contributor
timestamp: September 23, 2019, 10:02:08 pm
content: Quote from: ebastler on September 23, 2019, 08:40:46 pmWell, these are cheap and easy to get....No fun in that, had one.But to keep my mind busy, at the moment I am working on the smallest possible version of my relay clock, no matter the cost and with some SMD components ( I don't know how I'd ever get those soldered where they are supposed to go). Looks like everything would fit on 3 100x66mm PCBs... But each relay costs 0,85€ or so, since it's a special extra small omron one... PCBs - maybe 10€ with shipping, relays and parts - atleast 90€. Yay...Who knows where this will go

author: donotdespisethesnake
author_rank: Super Contributor
timestamp: September 27, 2019, 01:00:56 pm
content: I built a relay clock in a modular fashion, since 100x100mm boards are cheap, and typically you get 10 or more per order. I've got one board for each digit with about 20 relays each, and 6 smaller boards for each displayed digit. That's about 150 relays. I reduced the number of relays by using diodes as wired-or logic, maybe not a purist solution, but SMD diodes are a lot cheaper.The expensive part is buying relays, I managed to get a reel of surface mount relays for free, as well as a few hundred through hole relays.

author: Spemo
author_rank: Regular Contributor
timestamp: September 27, 2019, 03:27:20 pm
content: Quote from: donotdespisethesnake on September 27, 2019, 01:00:56 pmYep, the PCBs and other components are cheap to get, but the relays make everything expensive. especiall the smaller you want to build it.For example, I finished my Kicad project for the smallest possible version, with the smallest DPDT relays I could find.Cost of the PCBs: 10€ incl. shippingCost of transistors,resistors,capacitors, timing chip etc. 8-10€Cost for the 99 relays needed: 78€I really really want to build all of thee KiCad projects I have finished for the relay clock, but those relays escalate the price way too much.Also, my last handwired one failed today in an attempt to put new display modules in.A sad day, I thought it was going to last longer this time. But it shows exactly, why the handwired clocks are not worth building anymore.Have a nice dayDaniel

author: Cyberdragon
author_rank: Super Contributor
timestamp: September 27, 2019, 06:52:04 pm
content: QuoteNo excuse, welcome to electronics where murphy will eat your prototypes. You will have stuff not work, do weird crap, burn or blow up, exc.Figure out what's wrong and keep going.You are even using a PCB, there are plenty of people out there who do stuff point-point/deadbug. Clocks are pretty simple, even built out of discrete parts. Someone here built a color Pong game with sound and scoring using nothing but deadbug transistors and a copper ground plane. It's about the size of a dining room table.It is also possible to use a motor as a timing source as in this clock.https://thestuffwebuild.com/projects/electromechanical-digital-relay-clock/

author: tooki
author_rank: Super Contributor
timestamp: October 27, 2019, 01:00:15 am
content: Quote from: Spemo on September 23, 2019, 06:21:21 amJust a little FYI: Germankursiv= Englishitalic. (Englishcursivemeans “gebundene Handschrift”, or what we called “Schnürlischrift” in school here in Switzerland. :p )(Typographical pedantry: your design is actually anoblique, because it is only slanted, without otherwise changing the lettershapes as true italics do. But in common usage, we just call them all italics.)