[Arduino] Safety Tips while Modifying Home Electronics

[adamoutler]

Hi, I'm looking for electrical safety tips for modifying home electronics. I'm doing a series on developing an Android App and I'm an electronics tech so I tend to focus around fun electronic geeky stuff... You know, the type of stuff featured here on Hack A Day......

How to Build an Android App Part 5: Arduino ADK – Working with Digital Outputs – XDA Developer TV
How to Build an Android App Part 4: Illumination Software Creator – XDA TV
How to Build an Android App Part 3: Arduino Development
How to Build an Android App Part 2: Writing a Root App
How to Build an Android App Part 1: Setting up Eclipse and Android SDK

I'm going to do a video which will be referenced in a future episode. The idea is to make a video which shows how you can upgrade most home electronics devices by augmenting it with an Android device and an Arduino ADK. I will be modifying a small kids piano to be triggered with relays. I've decided to demonstrate with relays only because they can easily bypass existing switches and they are a good automation tool.

I want to emphasize that these same techniques can be used to control almost any type of touch panel electronic device, but I want to make sure people watching my videos don't cause fires or shock themselves... So I want you guys to help me out with some good tips for "developers"(people not expected to know electronics) who may want to start hacking electronics. I will link this thread into my video so my viewers can come here and absorb everything.

Safety while modifying electroincs with Arduino ADK

• Never work on a device with power applied.
• Always expect a fire and monitor for excessive heat buildup while testing operation. Be ready to disconnect power and have a fire extinguisher ready.
• Relays may be used in place of most momentary(switch) push buttons, but be VERY careful when replacing throw switches as they generally carry more current. This can be seen in coffee pots.
• Accept that while modifying electronics, you may damage them.

In my opinion: Choose a small form-factor 5V relay with a rating of at least 24VDC-120VAC for most USA home electronics. But I'm not sure about overseas ratings.

I'm expecting this to inspire quite a bit of android home electronics hacking/augmentation/automation. So, if you have some good advice for electrical noobs, please post it here... You know, Safety first.

[adamoutler]

A buddy of mine had this to add:

My opinion: don't fuck with anything that is directly AC-powered unless you know what you're doing (you do, I do, I still fear that shit). Mess with stuff that uses an external AC->DC power supply in which case you can often just do solid state without relays.

[semicolo]

If you have to play with AC, use optocouplers to prevent frying your android device and fuses to prevent fires.

[KillerBug]

If you play with AC, be sure to discharge the capacitors first...that should be #1 rule, or maybe #2 after "don't f**k with AC unless you know what you are doing". Actually, it is a good idea to discharge capacitors anyway, as even 12V DC can give a lethal jolt if a wire penetrates the skin and there are enough amps.

When soldering, use a quality iron...it doesn't have to be a $300 pro-level iron, but that $20 radioshack crap is just like asking for a fire. Also, be sure there is plenty of ventilation...lead-free solder fumes are even more toxic than leaded solder fumes. Never leave a soldering iron when hot, even if unplugged. Don't touch soldered connections for at least a few seconds after you think they have cooled.

Don't use electrical tape except for temporary test setups; use heat shrink tubing...it doesn't unwind/slide off of live wires. The stuff with the insides lined with heat-melt glue is a must if the wire will be anywhere near water (and generally a good idea anyway, as the air has moisture that can destroy wire).

Fuses and circuit breakers exist for very good reasons.

When using cutting and grinding tools, ALWAYS wear quality eye protection! Same goes for anything that might cause something to fly, such as hacksaws and hammers. You usually don't need to read the whole manual for a tool, but at least read the warnings...if nothing else, you will get a good laugh.

[Osgeld]

if the soldering iron falls, let it, don't try to catch it

caps hurt, even after hours of being unplugged

screwdrivers are not replacement fuses

if it has slots cut in the board around it, don't mess with it (high voltage arc gaps) unless you know whats up

wear eye protection, or at least squint / turn your head slightly while first powering on

solder / flux splatter is not as hot as bacon grease, don't let it freak you out

dont remove a filter cap and not replace it, then expect to not freak your wife out when the next one in line explodes at 1AM (stupid video card)

[st2000]

I'm going to wimp out and simply suggest not to build anything that deals with the house mains. Rather, OEM the hardware to do this and treat it like a black box. That is, 5 volts DC control signal goes in here which switches 110 volts AC over there. Done.