EEVBlog #425 - Mailbag  - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: February 15, 2013, 11:13:10 am
content: Dave.

author: LEECH666
author_rank: Frequent Contributor
timestamp: February 15, 2013, 11:46:20 am
content: I think the swedish post stamp showed rendeers and the three biblical Magi - Caspar, Melchior and Balthasar. Based on that my second guess is, that this is some kind of Christmas themed post stamp.Cheers,Florian

author: Len
author_rank: Frequent Contributor
timestamp: February 15, 2013, 05:04:57 pm
content: The Canadian stamp is for the Year of the Snake.http://www.canadapost.ca/cpo/mc/personal/collecting/stamps/2013/2013_jan_year_of_snake.jsf

author: LEECH666
author_rank: Frequent Contributor
timestamp: February 15, 2013, 08:34:36 pm
content: Sorry, but that snake stamp looks like a snake with a ball sack / scrotum atop of it's head to me. *chuckles*Cheers,Florian

author: Herr R aus B
author_rank: Regular Contributor
timestamp: February 15, 2013, 10:45:12 pm
content: The pacemakers might also come in handy next time Dave rants on proprietary designed power plugs and stuff :-)RegardsAxel

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 16, 2013, 01:28:51 am
content: As for the timer, the US versions are built the same way, just with a different plug/socket, a different gear ratio (due to the 50/60Hz difference), and a different dropping resistor.BTW, while the power loss in the resistor is pretty small, it adds up if you have a bunch of those timers around the house. Replacing the resistor with an X rated capacitor (calculate for the same impedance and measure the current, actual value used will be lower since the motor is inductive) will greatly cut losses.

author: bitwelder
author_rank: Super Contributor
timestamp: February 16, 2013, 08:40:04 am
content: Quote from: LEECH666 on February 15, 2013, 11:46:20 amYou're a little off with the guess...The Finnish stamp has reindeers but the three figures are actually the daughters of the Mother Goddess of Childbirth from the Sami shamanic religion (Sami are indigenous population living mostly in the northern Scandinavia).A series of 4 post stamps has been released to celebrate the opening of a Sami cultural center.Here is a picture of the whole sheet (which is shaped like a shamanic drum skin):http://3.bp.blogspot.com/-NjvqeoTfR9A/T6VGaOQXaSI/AAAAAAAAIwc/U3gLnjmIpow/s1600/Finnland+Kulturzentrum+Sajos.jpg

author: adam1213
author_rank: Regular Contributor
timestamp: February 16, 2013, 12:21:56 pm
content: In regards to the camera shown in the video:I wonder why they used a non standard charger plug for the camera.I don't know the specs for the camera / battery but based onhttp://store.jvc.com/product.asp?Model=BN-VG138UScapacity: 3.6V, 3750mAh. charging from standard USB instead would likely take 3-8 hours which may be acceptable. I wonder why they chose the non standard charger.

author: Winston
author_rank: Regular Contributor
timestamp: February 16, 2013, 04:36:24 pm
content: A way to get through your backlog of mail would be to open it up off-camera, select the coolest stuff to cover and then talk about it in the mailbag segment, covering it further in a tear-down segment if it merits it. Frankly, I've never wondered was was inside of an outlet timer being pretty sure I'd find exactly what you found.

author: opablo
author_rank: Regular Contributor
timestamp: February 16, 2013, 08:17:40 pm
content: Does anybody know how precise are the Mains 50/60Hz ?I know that some old microwave ovens were also using them to track time...How does that precision compares with an RTC chip with a 32.768KHz crystal ?

author: grumpydoc
author_rank: Super Contributor
timestamp: February 16, 2013, 08:33:30 pm
content: The spring loaded shutter which blocks access to the live & neutral until the earth pin is inserted is nothing special - that's how UK sockets work and so theyhaveto do it that way.QuoteOver long periods I think it's fairly stable - mains driven digital clocks used to use it as the reference frequency. Over short periods it does go up and down quite a lot. I'm afraid I don't have a reference to how accurate handy but I'm sure google can come up with something.

author: Bored@Work
author_rank: Super Contributor
timestamp: February 16, 2013, 09:28:36 pm
content: Quote from: grumpydoc on February 16, 2013, 08:33:30 pmhttp://www.mainsfrequency.com/has some information and a live display.

author: c4757p
author_rank: Super Contributor
timestamp: February 16, 2013, 09:34:09 pm
content: Quote from: grumpydoc on February 16, 2013, 08:33:30 pmNot just "used to" - I have an alarm clock bought this year that uses mains frequency. Companies are still cheap enough not to buy watch crystals. (The annoying part is that this means the best frequency reference it has when running off the backup battery, as far as I can tell, is an RC oscillator. It is five minutes fast after being unplugged for ten minutes...)

author: Ferroto
author_rank: Frequent Contributor
timestamp: February 17, 2013, 01:53:58 pm
content: I once got a cheap Chinese mp3 player for Christmas and the 12v plug pack used a Male 3.5mm audio jack. It was possible to plug 12 volts directly into the headphone jack.

author: SeanB
author_rank: Super Contributor
timestamp: February 17, 2013, 02:42:08 pm
content: Quote from: c4757p on February 16, 2013, 09:34:09 pmI have the same chipset clock, and opened it up and looked up the NMOS chip inside, then looded at the RC clock backup and adjusted it to run slow. Much better to have a few minutes behind in a power cut as it is a lot easier to go forward rather than going all the way around the minutes when the power is back. Luckily mine had a trimpot for this.At the same time I removed half the board with the radio side and shoehorned an OPTO22 hockey puck SSR inside to control the bedside light. I do not need a heatsink on this 20A unit when it is running a 32 candlepower lamp.

author: c4757p
author_rank: Super Contributor
timestamp: February 17, 2013, 03:42:22 pm
content: I would rather it run fast. If the power is temporarily lost at night, it will wake me early, not late.

author: SeanB
author_rank: Super Contributor
timestamp: February 17, 2013, 06:00:12 pm
content: You adjust it till it only loses a minute an hour....

author: c4757p
author_rank: Super Contributor
timestamp: February 17, 2013, 06:10:50 pm
content: Mine didn't have a trimpot (I'm sure that's why it was off so much to begin with) and I really didn't want to spend time modifying a $5 alarm clock. (In the five years I've been in this house we have only lost power once, so it's not a big deal. I'd just use a different clock if it really mattered.)

author: tom66
author_rank: Super Contributor
timestamp: February 19, 2013, 08:26:03 pm
content: Our plugs in the UK are well designed: that shutter is a legal requirement, and directly inhibits attempts to access mains power using e.g. a screwdriver. (You need at least two...)

author: alanb
author_rank: Frequent Contributor
timestamp: February 20, 2013, 02:26:49 pm
content: QuoteIn the UK the short term accuracy is within +- 1%. This is a legal requirement of the licence granted to the National Grid. If it looks as if the frequency is falling outside that limit they either bring more capacity on line or shed some of the load.

author: robbak
author_rank: Contributor
timestamp: February 21, 2013, 04:31:04 am
content: Quote from: opablo on February 16, 2013, 08:17:40 pmIn the short term, as others have stated, it varies quite a bit. But in the medium term, they actually cycle count, compare it with UTC standard, and adjust. So, long term and baring blackouts, a mains synced clock will never drift.