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Author Topic: 220V module - Adjustable countdown timer 99 Min with Led display (But Caution)  (Read 342 times)

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Offline Kiriakos GR

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I am in need for a simply adjustable countdown timer up to 99 Min with Led display, and also I did not wanted push buttons and I did discover one circuit (module) this capable for 0~99 seconds and of 0~99 minutes by jumper settings.
Adjustment this is possible due a 500K Ohm potentiometer and supposedly only additional part needed this is an simple trigger switch (button).
 
By finding the right module on eBay, I did discover two versions, first one was powered by DC, second was powered directly from Mains 220~230V
By looking the pictures I though that 220V version this was including a mini transformer (12V AC), pictures was unclear all that I could see this is some grey or black part at the size of PCB transformer.

But the very truth this is that I was fooled  :P , makers of such PCB they use in line capacitor and few 100K resistors so to step down the voltage.
My own plan was and this is about me to make a fancy enclosure, use a full size potentiometer and a regular mini switch as  seconds/ minutes selector.
But ... But .. But .... this circuit as is this does not offer isolation to mains and I consider it as quite dangerous as is.

I did paid and ordered the module prior becoming aware of entire truth.

Either way this upcoming project will move forwards and I will modify it so an true transformer this to do the step-down work, so usability and safety both to be restored. ;)

My advice to people thinking of getting such specific module, they might worth getting the one with DC input instead the one supposedly ready for 220~230ACV because the second does not qualify as is speaking of safety.

I am an electrician  :) I can modify it to make it suitable for my project and requirements, but either way and in both cases you will need to use a real transformer and there is no cost savings no matter of what you will select.   

In the positive side of things, module which I did select this is much advanced than common 555 chip timer,  last two pictures at the bottom, they are from cheap 555 timer PCB but the point this is you to see finest detail of step-down capacitor and resistors circuit.   
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Offline Kiriakos GR

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Today I have excellent news !!  8)

I did discover the maker of those at Taobao market place.
His product design options now include and JK13-TN  circuit this using real transformer.

Transformer specification:  12V 1VA 
Dimensions : length 85mm x width 45mm x height 30mm

Model which I did purchased this is JK13A, I must admit that this maker it is very honest, he does pass the advice at Chinese buyers them to select JK13-TN for increased safety and long term reliability.
Unfortunately his products are not widespread to eBay market place.   
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Offline Kiriakos GR

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Gentlemen ... !!   8) 

After some waiting for parts and taken care of some other projects of higher priority, I am today presenting my very own version of timer with analog control.
My plan from the beginning was to compose this gadget with parts that I all ready own, most to all they are quality items.
The enclosure for example this is made of special unbreakable plastic which tolerates high temperature too.

Regarding electrical details, I did use one 12V 400mA transformer ( enclosed AC power adapter - Wall Plug).
Female Schuko plug ( part of a dead UPS) with VDE certification.
Fuse holder this secures input 220V with 7A fuse, and this translates that loads are not expected to be higher than 1800VA.

By removing two resistors and this big capacitor (step down circuit to 12V) connection of regular transformer was easy.

Regarding functionality, this circuit it quite accurate at 0~99 seconds, I have not tested yet 0~99 minutes range.
Only noted technical issue of this module this is LED display luminosity when this working which is lesser than when this is at stand-by mode.
Even so this module works well and I am happy !  :) 

Full size potentiometer this offers very good control, and selection of time interval this is very easy to do.

By having pressed this KEY button and by connecting the circuit with AC power, this module starts operating right away and stops at time preset.
Other option this is powering up the module, and use KEY button when you like so.
 
Currently I have two good examples of applications for it.   

1) Battery charging with timer.

2) Power consumption comparison (by power measurement) of two electrical loads (appliances or light bulb or other loads) in the unit of time.
In this setup one digital power meter will be connected at input.     

Practically addition of this timer gadget at my workshop this makes it now as complete regarding testing gadgets for product reviews or all sort of electrical evaluations.
Enjoy the pictures and steal ideas if you can  :P  ;D
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Offline Kiriakos GR

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Product testing and more pictures  ;D 8)
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Offline Kiriakos GR

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In conclusion ...

Module price : €3.55 EUR 
wire wound potentiometer price : €2.47 EUR
Total  € 6.02

By having now awareness of total part list this is not a cheap project, either way what counts more to me this is: robustness - easy to use - long life cycle - and repairable .
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