Author Topic: TOPIC: SAFETY QUESTION (again)  (Read 1489 times)

square

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TOPIC: SAFETY QUESTION (again)
« on: July 25, 2016, 11:08:10 AM »
After receiving the kit, I was wondering about safety. The following is perhaps the only question I found in the forum about this topic: http://www.makeymakey.com/forums/index.php?topic=15190.0
Then, I read some old answers to the FAQs where it is said:
Quote
The voltage is similar to that provided by 3 AA batteries (or in technical terms, 50 microamps);
enough electricity to have a lot of fun, but not enough to do any harm.

and I also came across the schematics of makey_makey-v12.
I am puzzled about safety because I recently had to do with a similar USB-powered device. Usually, ground is shared between the device and the PC and it seems makey makey makes no exception.
The PC may be grounded or not. If a person closes one of the makey makey's circuits and he is isolated from EARTH, I don't think there is any harm.
However, if
1) a person is not isolated and he closes one of the makey makey's circuits
2) a fault happens in the PC which makes GROUND become LIVE
the PC is shorted to EARTH through that person.
If this holds true, in my opinion, it should clearly be stated that
IF A PERSON IS NOT ISOLATED FROM GROUND (read "BARE FEET"), HE CAN STILL USE MAKEY MAKEY SAFELY IF HE SIMPLY CLOSES THE CIRCUIT WITH ONLY ONE WIRE WITHOUT CONNECTING HIMSELF TO MAKEY MAKEY'S GROUND (EARTH).
Notice that it should make little difference if the PC is grounded or not, I believe.
Hope to receive comments and opinions.

« Last Edit: July 25, 2016, 11:12:43 AM by square »

Liam

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Re: TOPIC: SAFETY QUESTION (again)
« Reply #1 on: July 27, 2016, 05:35:56 PM »
Hey Square,

That's not accurate.
A Makey Makey user is connected to a high impedance input on the semiconductor and 5V power via a large 22 Megaohm resistor. That's what the user grounds and is why the current flow is so low, i.e. not a short.

Makey Makey is very safe.  It's powered by a USB connection, not AC current.

Something to note is that we experience more electrical charge with normal daily activities like walking on carpet or wearing polyester clothing than using a Makey Makey.

Makey Makey uses resistive touch sensing that is present in many consumer electronic products and is FCC compliant.

Here are some considerations to follow when using Makey Makey:

- Makey Makey should be used according to its intended use via the USB cable provided to a USB compliant port.
- Never connect Makey Makey to an AC outlet.
- If product is damaged or broken, please discontinue use and contact Makey Makey support.

I hope this is helpful and relieves some of your concerns. Please be in touch with any other questions.

square

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Re: TOPIC: SAFETY QUESTION (again)
« Reply #2 on: August 04, 2016, 07:55:40 AM »
Agreed: MAKEY MAKEY is safe. That can be said after some experiments in water...
And
Quote
IF A PERSON IS NOT ISOLATED FROM GROUND (read "BARE FEET"), HE CAN STILL USE MAKEY MAKEY SAFELY IF HE SIMPLY CLOSES THE CIRCUIT WITH ONLY ONE WIRE WITHOUT CONNECTING HIMSELF TO MAKEY MAKEY'S GROUND (EARTH).

should have been written as
Quote
IT IS SAFER IF A PERSON...

since 5V is a very low potential and GND is not allowed to invert to 120/220V.
In fact, this is the schematics I referred to (http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Dev/Arduino/Boards/makey_makey-v12.pdf)
I am not a guru of electronics but GND is shared with the USB and GND is what the user touches. Current is low into the board due to its high input impedance but it might be higher through a person (though it is limited by design). Anyway, under normal circumstances I totally agree that MAKEY MAKEY is SAFE. Perhaps, it might be even SAFER if a person not isolated from EARTH would not touch the board GND. But even this is usually (99.9%) SAFE.
« Last Edit: August 04, 2016, 08:05:48 AM by square »