Kit review - Generic AliExpress Digital Clock. - Page 1
Forum section: electronics / beginners

author: hamster_nz
author_rank: Super Contributor
timestamp: September 12, 2019, 10:34:20 pm
content: I wanted to give others the opportunity to play with electronics, and looked for a project that was inexpensive, useful, funtional and achievable. I settled on an DIY Digital Clock kit.https://www.aliexpress.com/item/32972008419.htmlGood points being:- It is actually a useful clock- It is powered by generic USB supply- It has a case- The case is clear, so you can admire your creation.- Dirt cheap - US$6.25 with free shipping.- Uses through-hole parts (which is also a bad thing)- It is complete, including cable.Delivery:Ordered on the 26th Aug, arrived on the 11th FSeptember. Can't complain about that.Building:Instructions are not in English, but everything is clearly labeled on the PCB, and the resistors have the values stamped on the paper tape. Just have to be careful to allow enough leads on the Crystal, LDR and thermister so you can fold them flat to the PCB.Following the usual pattern of working from lowest sitting parts (battery clip and resistors), to the highest ones (Switches and 5mm power jack), leaving the displays for last.Before the displays are soldered in place, the board can be tested with them press-fitted. Once soldered on you will not be able to fix up and errors/bodges without removing them.The RTC and micro controller are socketed, which is nice.Testing before mounting the displays:- Checked that all segments lit on at least one display (so the segment driver works).- Checked that all displays light at least one segment (so the segment transistors work)- Checked that the buttons did something.Mounting the displays:Three of the displays go one way up, one goes upside down. It would be very easy to not see the "dot" on the silk screen and get this wrong. Would be very frustrating.The case.The clear laser cut acrylic case is very cunning. Goes together with nicely.Summary:Seems to be a great rainy-day afternoon project. Recommended for a keen beginner, with a little help to check things before the displays are soldered.Image is the finished produce, and a few of the kits behind it.

author: magic
author_rank: Super Contributor
timestamp: September 13, 2019, 06:30:17 am
content: Quote from: hamster_nz on September 12, 2019, 10:34:20 pmIf it's accurateI have seen one cheap-ass clock which could be tuned quite a bit just by varying supply voltage

author: hamster_nz
author_rank: Super Contributor
timestamp: September 13, 2019, 06:49:47 am
content: The timekeeping is on a DS1302, with a coin cell battery, and looks to be OK after 24 hours.The dimming when the lights are off (sensed by an LDR) is actually pretty good - more clocks should do that.

author: wilfred
author_rank: Super Contributor
timestamp: September 13, 2019, 07:11:31 am
content: Is that the same clock that BigClive did a video on? He showed (at 7 seconds) the instructions in English.

author: bd139
author_rank: Super Contributor
timestamp: September 13, 2019, 07:16:41 am
content: Looks pretty good actually. Thanks for the review. I might order one.

author: OE2WHP
author_rank: Regular Contributor
timestamp: September 13, 2019, 07:29:06 am
content: I've built one with my 10yo daughter on a rainy afternoon. She loves this clock. Setting up time/date/alarms however is a bit annoying.

author: hamster_nz
author_rank: Super Contributor
timestamp: September 13, 2019, 07:43:40 am
content: Quote from: wilfred on September 13, 2019, 07:11:31 amSame kit, different instructions. Sounds like BigClive's instructions were a bit rough!

author: bd139
author_rank: Super Contributor
timestamp: September 13, 2019, 07:47:12 am
content: If you want rough instructions buy one of those AM radio kits from China. Not only are they mostly in Chinese but once you’ve figured them out you realise they aren’t for the kit that they ship with

author: tooki
author_rank: Super Contributor
timestamp: September 13, 2019, 11:39:35 am
content: I've built a few of these, and the accuracy is all over the place. It can be hard to see in 24h, but when you're having to adjust a clock every week or two (especially if it's going fast, meaning you have to cycle around since they have no "back" button), it gets old real quick.I now only get the kits with DS3231 RTCs, which have proven to be exceptionally good. I don't know what causes the DS1302/1307 based clocks to be so unpredictable in their accuracy, but at some point, it just ceases to be fun...

author: Bud
author_rank: Super Contributor
timestamp: September 13, 2019, 01:03:56 pm
content: 'Cause those DS1302 were made in a Shenzhen shop on a back alley on a rainy day?

author: magic
author_rank: Super Contributor
timestamp: September 13, 2019, 01:43:02 pm
content: It can be an exercise on its own to measure ppm/°C, ppm/V, ppm/pF and "pull" them to the right frequency

author: bd139
author_rank: Super Contributor
timestamp: September 13, 2019, 01:45:17 pm
content: Quote from: Bud on September 13, 2019, 01:03:56 pmI think they were the ones that ended up in a large sack thrown out the back because they were out of tolerance.Quote from: magic on September 13, 2019, 01:43:02 pm

author: JackJones
author_rank: Regular Contributor
timestamp: September 13, 2019, 01:53:05 pm
content: Quote from: tooki on September 13, 2019, 11:39:35 amThey use an external crystal which is probably the cause. I've used a DS1307 with a crystal from a random seller before and it was at least +- 1 minuteper day. With a crystal from a reputable seller the results were much better.And I agree, DS3231 is the way to go. Unless you get a dud. Better buy them from a reputable seller too!

author: wraper
author_rank: Unknown
timestamp: September 13, 2019, 01:55:09 pm
content: Quote from: Bud on September 13, 2019, 01:03:56 pmDS3231 has built in TCXO but DS1302 uses external crystal which most likely is of questionable quality. Not to say that likely they just use some random crystal instead of with required 6pF loading capacitance.