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Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

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Re: Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

#181

Post by stavros »

butvacuum wrote: post #175
stavros wrote: post #169

Earlier quoted context omitted.

Comes out to $6 per part for me, with shipping, which is much more than I'm willing to pay.

and it'd still be $6 for 600. It's as if people have never had shipping itemized before. The only reason aliexpress shopping is cheap is because the rest of the world foots the bill. Unless somebody has finally removed China's "Developing Country" status thats gotten them essentially free international parcel service for the best part of 100 years.

Yeah OK, but if I only want 5 pieces and I have to choose between $5 or $30, I'm not going to think about the geopolitical situation, I'm just going to get the cheaper one.

Re: Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

#182

Post by bArray »

VladVladikoff wrote: post #178

I don’t understand why it needs to neurotically check so frequently? 30 times a second seems like a lot of hammering on the NTP server. Am I missing something here? Some physical reason why that is necessary perhaps?

> The ESP8266 reconnects to the NTP server every 15 minutes which keeps the clock accurate.

It doesn't seem to be hammering the NTP server 30 times a second.

Re: Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

#184

Post by wat10000 »

tanvach wrote: post #115

Related - we have an atomic Seiko wall clock expecting to have the time automatically adjusted by the WWVB LF atomic clock broadcast. Turns out, the signal is very weak where we now live. Manually setting the time on these atomic clocks is a HUGE pain (beware!). Turns out it's possible to emulate the atomic clock signal quite easily with a Raspberry Pi, or in my case I put together Arduino code that can emulate atomi…

Supposedly you can do it with a stock smartphone or tablet by using the audio hardware to deliberately generate RF noise that works like a WWVB signal. https://github.com/kangtastic/timestation

Re: Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

#185

Post by insane_dreamer »

sowbug wrote: post #9

If you like this but don't want to get your hands as dirty, have a look at the Crazy Clock: https://www.tindie.com/products/nsayer/crazy-clock/ I got one for my daughter. The erratic ticking eventually became a distraction when she was studying, so we have retired it for now. But we got a lot of amusement out of it.

Fun! I might get one of these to put together with my son; a lunar clock would be interesting.

Re: Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

#186

Post by the_fall »

teraflop wrote: post #5

Cool project! The most interesting part, IMO, is the "SRAM with EEPROM backup" chip. It allows you to persistently save the clock hands' positions every time they're moved, without burning through the limited write endurance of a plain old EEPROM. And it costs less than $1 in single quantities. That's a useful product to know about.

Meh. The room-temperature endurance of modern EEPROMs (e.g., ST M95256) is something like 4 million cycles. If you use a simple ring buffer (reset on overflow, otherwise just appending values), you only need to overwrite a cell once every 32k ticks, which gives you a theoretical run time of 250,000 years with every-minute updates or 4,100 years with every-second updates.

Re: Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

#187

Post by ComputerGuru »

This is more resourceful than what I once did, which was set up an atomic clock "repeater" to get analog atomic clocks (one in each room) in a site to actually receive the signal in a 1930s structure made of solid brick and concrete blocks.

Except it wasn't a repeater so much as it was a MITM fake, with an rpi connected to an sdr-like system to generate a fake WWVB (iirc?) based off an NTP clock.

Legality was technically questionable, but since the signal didn't really leave the site perimeter (or even the building, really), I think it was ok.

Re: Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

#188

Post by ComputerGuru »

pjc50 wrote: post #170
sowbug wrote: post #26

Earlier quoted context omitted.

I'm not sure if this is the same technology, but regardless it's also cool: https://www.adafruit.com/product/1897

FRAM is extremely neat on paper, combining SRAM ish speeds with non-volatility, but adoption seems to be low. Possibly due to scaling issues. I've had a FRAM-based TI MSP430 in my random parts drawer for about a decade.

That was my first FRAM experience, too. Good chip, good times. Insanely low power draw!

Re: Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

#189

Post by opello »

pwg wrote: post #152
stavros wrote: post #142

Earlier quoted context omitted.

Has anyone found the chip on AliExpress? I only get unrelated listings with that part number, but this is a pretty interesting chip I'd like to get a few of. An alternative would be a supercapacitor and a voltage divider connected to the ADC pin of the microcontroller. When the 5V rail dies, the supercapacitor can hold 3.3V for a few seconds while you write everything to the EEPROM.

$0.77 US single piece cost on Digikey: https://www.digikey.com/en/products/detail/microchip-technol... And, at least with Digikey, you can feel like you actually get the real part vs. some low end clone knockoff.

That's the TSSOP version, while the DIP is $0.92:

https://www.digikey.com/en/products/detail/microchip-technol...

I'd prefer even the SOIC version which is $0.69 if I'm soldering it:

https://www.digikey.com/en/products/detail/microchip-technol...

but the author used the DIP in a holder/socket on the perfboard.

Re: Converting a $3.88 analog clock from Walmart into a ESP8266-based Wi-Fi clock

#190

Post by aidenn0 »

KaiserPro wrote: post #91
mlhpdx wrote: post #85

Earlier quoted context omitted.

In a perfect world, yes. But mechanisms aren’t perfect and it’s entirely possible if not likely that steps will be missed as friction increases over time and things wear. I’m not saying these things matter much in this context. The clock will still be far more accurate than purely mechanical version. And, re-synchronizing it is as trivial as turning the knob, just as you would for the all mechanical mechanism.

its a fairly reliably stepper motor system. You're right it will degrade over time, you'd be surprised how many steps it can do before it degrades.

I had a clock where the second hand was not properly balanced and it would miss steps fairly reliably in the second-half of the minute (when the heavier side of the hand was going up). I added some tape to the counterweight to fix it.
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