Electrostatic Discharge
Astrogirl1usa
Posts: 8
I just bought the Basic Stamp Discovery Kit and the BoeBot kit for my son (almost 14) for Christmas. I've been reading up on electronics in general and I've come across a subject that worries me. Will my son need something to ground himself with while working with the BS2 and other components? Also, what is meant in electronics terms, by 'mains'? I saw some references elsewhere pertaining to grounding to the mains. I've searched this forum and found nothing I could use. Maybe this stuff is covered somewhere in the documentation that comes with the kits, but as it is a Christmas present; I haven't opened anything. We live in an apartment that is almost entirely carpeted. If electrostatic discharge is going to be a problem; what can we do about it? Mind that I've blown all my money on the kits already, is there a fairly cheap fix for this? If you read this after Christmas day, please still respond as my son won't be home until the 28th, so I have a little time to do whatever needs to be done about this, if anything. Thanks
Comments
The need for grounds while working with electronics like the Stamp Discovery Kit depends on the likelihood of static electricity. This time of year, it tends to be at its worst because of the dry air inside. It helps to have some humidity in your home. It helps to touch a metal lamp that's grounded, like with a 3-prong (grounded) power cord, when you sit down to work on electronics. You can buy relatively cheap antistatic mats. The question is where to connect them. A radiator or baseboard heating unit should be grounded. The 3rd pin in your electrical outlets should be grounded.
I'd opt for a humidifier and a metal table lamp with a 3-wire cord. The lamp will be good for a work area anyway and the humidifier will reduce static and be healthier for you in general. See how much difference the humidity makes first before worrying about an anti-static mat.
However, I once worked in a nice new building with synthetic carpet and was getting sparks all the time. Even keyboards were getting zapped.
So the simple answer may be just to not work in an area with carpet. Even then, it depends on the type of carpet - wool is better than synthetics. Do you get a zap when you scuff your feet then touch something metal?
One simple practical solution - before you start soldering a chip, just touch something metal that is earthed. Eg a computer case. And don't scuff your feet on the carpet while sitting at the chair.
Is the kit for you or your son? Are you allowed to start working on it now? (I would be. *grin*).
These guys are correct about just touching something that's grounded before beginning to work - the metal case of a computer, for example, or the screws that hold the face plate of a household electrical outlet. Mike's idea about using a lamp with three prongs is a good idea. Keep in mind that some chairs can generate static if you wiggle around in your seat too much. I've got a chair that would have stood Ben Franklin's hair on end. Whatever you do, don't just hook a wire from your kid's wrist to something like a radiator, etc. There are special wrist straps that you can connect to a radiator, etc. and these will keep you grounded all the time but they are made in such a way as to prevent you from getting a lethal shock in the event you touch something that's hooked to the mains. You can get these kinds of wrist straps probably at a local Radio Shack for maybe even less than the cost of a three-pronged lamp.
http://en.wikipedia.org/wiki/Antistatic_wrist_strap
Have fun!
Also, using a grounded metal table is much better than a wrist wire with kids. And using batteries rather than 120VAC is far more sensible too. The problem with grounding around AC is that you can get between the 120VAC and ground. Many advocate a wrist wire that includes a 1 meg ohm resistor in order to avoid serious shock. You could ground the table through a 1 meg ohm resistor as well for safety's sake if you are working with AC. The resistor can be 1/4 watt or larger - a very cheap component.
The proceedure is to simply touch the table before you work with your electronics. But the metal table also can be a disaster if you set a powered printed circuit board directly on it. Short circuit damage can occur. So a plastic matt for such projects is another requirment.
As you can see, the problem is and always was that electricity is unknowing and unforgiving in how it seeks a circuit. So it is best to just keep projects for kids to low voltage, battery powered devices and present safety as they learn more.
I also sit in a chair, on carpet, or on a "chair plastic mat", I had horrible static zapping coming from my ears. See I wear headphones, large DJ studio type, so the static jumps from my ears to the headphones.
Most movement of materials upon each other is bound to generate static.
Making entire surfaces out of grounding material, (a metal mat under the chair) or a metal table surface.
Most people rest their arms on a table, making just the corners a ground would help.
I wired up a loop of copper wire and wrapped it around the corner of the desk many times to create a large grounding "pad" that i could momentarily touch.
I don't like grounding straps, grounding floors, etc.. I have had too many situations where I was working on high voltage, and mains, and accidentally included myself into one leg of one of the phases.
Its tingly, but if your not grounded at all, and your chair isn't, and your desk isn't, and you don't wear a strap, etc... well I didn't die because of my choice to not ever complete the circuit.
A better choice for static "especially when working with anything electronic" is to have a surface that you can momentarily touch to discharge any static built up. In 3.3v situations you won't get shocked, but the habit you develop by using bad ideas in your skill, just might zap you in the future.
This method combined with using one hand while working on electronics also might keep someone alive. Again 3.3v won't shock you, but developing good techniques and habits when it comes to grounding is the best.
If its human, don't complete the circuit, make the human a wire to no where.
Don't have anything grounded, except a single surface on the desk that you touch periodically. Having the whole table surface ground might be bad for a kid, due to making it a huge surface to short to.
Here in Taiwan, the humidity is generally 60% or so and the floor is ceramic tile. And so I've not bothered with any protection at all. All the heat I've got is one 1200 watt unit by my desk.
Anti-static wrist strap
Anti-static gloves
I think a few of people got pretty technical on this subject, forgetting that we are trying to answer this for a Mom. May I suggest a visit to the Radio Shack web site on Anti Static devices:
http://www.radioshack.com/search/index.jsp?kwCatId=&kw=anti%20static&origkw=anti%20static&sr=1
and then go in to talk to them about the possible static problems.
Jim
You need a grounded 3 - prong outlet for the most likely success. If you want to do an easy and safe job, the central screw that holds the cover plate on is supposed to be grounded and a wire can connect to the loosened screw and then re-tightened - no need to go inside or to poke wires into holes. There are many other ways to do this, including just connecting your anti-static wire to any cold water pipe (hot water pipes may not be grounded).
Guys here tend to be very technically savy. Sometimes the focus is not adequate for the safety of a complete novice. It you are unsure of safe wiring practises in a home environment, get someone who can test for a good ground and do a good safe job. We all would rather not see you have an incident due to some misdirection.
Well, you can find them at different price and quality at eBay, these cheap are made and ship mostly from China and also competition at eBay hold the price down... and yes I have purchased from these store at eBay so many times, not only me but also most of our friends here at Parallax forum has purchased some or many things from these eBay store. Merry Christmas!