Safety Precautions


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Safety Precautions to ensure that your KeyMaker Board and ThinkPad are not damaged

In order to avoid damage to your KeyMaker Board as well as the ThinkPad you are using it on, there are certain precautions you MUST observe.

If you ignore these precautions you will join the 3% of customers who bought a KeyMaker board - ignored these precautions and damaged their KeyMaker Board  by being careless - then had to pay to have it replaced - and lost a lot of time in the process.

Your KeyMaker has electrical contacts on both sides, you must ensure that no part of your KeyMaker USB board comes into contact with any conductive surfaces such as bare metal or bare wires.

You should place down a piece of paper and place your KeyMaker USB on top of it in order to avoid any electrical contact which may damage your KeyMaker.

There is no danger of receiving an electrical shock from your KeyMaker USB as the highest voltage anywhere on the board is 5 Volts which is a safe voltage to touch.

If you prefer you can place your KeyMaker USB board inside an Anti-Static  plastic bag during use, the board does not get warm at all, so there is no issue with ventilation.

The same precautions apply to your ThinkPad when you are performing any operation and BEFORE your ThinkPad is switched ON, you must ensure that nothing can short out by coming into contact with other parts, you can use sheets of plastic or plain paper to make sure things remain electrically isolated.

You MUST NOT allow the SDA and SCL leads from any KeyMaker KMX1 or KMX2 to come into contact with ANYTHING other than the correct SDA and SDA EEPROM connections points and ONLY AFTER;

You have traced the wire you are using for your probe right back to the label on the I2C header on the KeyMaker board which reads SDA for YOUR SDA lead and reads SCL for YOUR SCL lead.

You have absolutely confirmed that you have correctly identified the SDA and SCL connection points on your ThinkPad System Board.

3% of customers who purchased a KeyMaker Board have somehow managed to damaged their KeyMaker board.

NOT ONE of those customers can tell me exactly what he or she did to damage it.

I have tried all sorts of seriously ridiculous ways to damage a KeyMaker board and I have NOT BEEN ABLE TO DAMAGE ONE !

I only tried MILDLY STUPID THINGS like connecting a solid 9 Volt source to SDA and SCL - theoretically that should have damaged the I/O pin on that KeyMaker powered from 3.3 Volts, IT DIDN'T.

Your KeyMaker board is a delicate piece of equipment, treat it with respect.

Do NOT experiment or connect to anything if you are not certain you have the correct connection points identified.

There are voltages much higher than 3.3 Volts inside your ThinkPad, in fact up to 20 Volts. 

20 Volts is not a danger to YOU but it is to the KeyMaker KMX1 or KMX2.

Connect SDA and SCL leads ONLY if you have double checked and are CERTAIN you have correctly identified SDA and SCL connection points

The above is VERY IMPORTANT - don't ignore it else you WILL damage your KeyMaker KMX1 or KMX2 board and that is expensive, wastes a lot of time and is not much fun.

The 4 leads from the KeyMaker I2C header connector are VCC, GND, SCL and SDA.

GND is connected back to GND on your mini USB connector and onto your PC or laptop.

VCC comes from the 5V DC supply from the Mini USB cable connected to a PC or Laptop, it then passes through a 3,3V regulator and a self resetting Pico fuse, so it is reasonably well protected should you accidentally short it out, in 99.99% of use we do not use the VCC lead anyway.

You need to take care with the SDA and SCL leads as they are NOT protected and can be damaged

If you are careful and NEVER connect SDA or SCL to anything other than the SDA and SCL connection points of the EEPROM inside a ThinkPad no damage will ever occur.

However if you are careless and connect either SDA or SCL to GND or VCC on your KeyMaker Board or some higher voltage point inside your ThinkPad you will damage the KeyMaker SDA and or SCL I/O pins.

The reason is that the SDA and SCL I/O pins connect directly to pins on the Microprocessor on your KeyMaker USB.

The SDA and SCL I/O pins MAXIMUM SAFE DC Current is 40 mA, that is 40 thousands of an Ampere, a VERY small amount of current.

If you exceed 40 mA you will damage the I/O pin and your KeyMaker will not function.

You will exceed 40 mA if you directly connect SDA or SCL to a voltage source higher than the 3.3 Volts powering your KeyMaker.

Therefore you must double check that you do indeed have the correct lead and you are about to connect it to the correct connection point BEFORE you actually connect it.

If you want the luxury of being careless, make serious mistakes connecting to an EEPROM and not cause damage, there is a way you can protect your SDA and SCL I/O pins so that they cannot be damaged even if you accidentally connect either to  a voltage SLIGHTLY HIGHER than 3.3V, this will NOT save your KeyMaker if you do something really dangerous like connecting the leads to high voltages!

The protection consists of 2 x 180 Ohm resistors. Very inexpensive insurance.

One 180 Ohm resistor is connected in series with the SDA lead.

Another 180 Ohm resistor is connected in series with the SCL lead.

Or you can use the KMX-LCD which has the 2 protection resistors already fitted.

Below are photos of how I modified my 4 way I2C lead to make it safe against accidental contact with GND or VCC


The original 4 way lead, 2 x 180 Ohm 1/4 Watt resistors


Cut out a length of lead from the SDA and SCL leads and solder 2 resistors in series, I used heat shrink which must be threaded onto the cable BEFORE soldering


Heat shrink in place


Clear sticky tape wrapped over the heat shrink for added strength

The modified 4 way I2C lead connected to KeyMaker USB board



I make no warranty that any of my information is correct, or safe, or does or does not breach any warranty clause,  or anything else, it is up to you to decide if you will follow all or any of the instructions to recover the Supervisor Password from a TP. It is up to you to decide, I am not responsible for the results or for any consequential or incidental damages whatsoever.

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Last updated on Monday, 12 December 2016 06:31:09 PM  

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