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> Mec Turtle Light Pcb, Reverse engineering
diople
Posted: February 16, 2016 02:40 am
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Hi guys,

I'm new to the PCB boards. I want to reverse engineer a Mec Turtle light and set one up with components on a bread board. I hope this will let me understand how to make a mini flashlight.

As far as I can tell, it is 2 resistors, a diode and then this big black circle. I don't know if it is a transistor or an LED driver. any help is appreciated.

I haven't figured out how to upload a picture, but here i a link to it. If anyone can tell me how to upload a picture I will.

My background is mechanical engineering.

https://thelazyrando.wordpress.com/2011/04/...ot-bike-lights/
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kellys_eye
Posted: February 16, 2016 08:19 am
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The 'big black circle' will cover an on-board (chip-on-board) device. This is a 'naked' integrated circuit with a blob of epoxy covering it so it will be indecipherable under normal use. That said, it's not difficult to make your own circuit to achieve a particular function.

What is it that you want to do? Just flash LEDs?


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diople
Posted: February 16, 2016 01:12 pm
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Thank you for the timely reply.

I recently acquired a 3D printer and wanted to design and build my own small led light. I started looking at the different designs (simple 1 resistor circuit, IC led driver and circuits built using transistors) but was a little overwhelmed with the different choices. In order to get a better idea of what an established design looks like, I took apart a MEC turtle light, hence my question about the blob. It looks like I should go with an IC led driver. I will then set it up on a breadboard to prove my design.

Once the design is completed I will design a PCB in Eagle (Iím sure Iíll be on here again since I have never used it before) and get it printed. Integrate the components and hopefully have a customized mini LED light.

I may wish to mess around with the design a bit. It is my understanding that an IC will allow the different functions, as flash, steady beam, etc. Is this correct or am I wrong?
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kellys_eye
Posted: February 16, 2016 01:40 pm
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You need to understand the principle behind the way 'bike lights' work - they are seldom just LEDs that are switched on but instead are LEDs driven by a short (but large) pulse of energy that increases the light output exponentially.

LEDs have a steady-state light output of so-many-lumens at a given current hence the simplest arrangement of driving them using a single resistor.

The maximum light output can be increased by applying a large pulse of short duration such that the TOTAL energy in the pulse remains within the capacity of the LED device but the PEAK levels are substantially higher. The circuit used to achieve this is a 'pulse generator' or 'pulse width modulator'. Both types of circuit can be built using conventional components (resistors, capacitors, transistors etc), integrated circuits (like the type 555) or by software routines written to deliver the same shape of pulse via a programmable IC (microprocessors etc).

If you google pulse generator and/or pulse width modulator you will find many examples in the various construction methods mentioned. Pick and chose the version you wish.

But do remember that you're re-inventing the wheel and that there are a zillion examples of what YOU want to do already out there. Fair enough if what you're doing is a simple learning exercise but if you fancy design/manufacture you've got some serious opposition out there!

Best advise would be to find a compact commercial version and change the LED/LED arrangement to fit a case of your own design and see where it takes you.





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