NickReiser's Biped

I made a website for my project a week or so ago, and forgot to post it.

You can access it below:

Try not to laugh too hard.
I won’t be held liable for any ruptured spleens, when you do.


I dont get it.

I think the ideas was that he was pointing at the “www” button under his name. I hope this little misunderstanding isn’t a preview of the quality of web design we should expect Nick! :wink:

I checked it out… I had to look away, my eyes were burning. :stuck_out_tongue:

Let’s see some images of that bot! :smiley:

Hey Nick, I checked it out, and my eyes burned too.

Hint: In your picture, it appears that you’re keeping your SSC-32 in an ordinary zipper bag. I would advise against this, since it has static-sensitive parts on it. And don’t put any ‘good’ electronics in that Tupperware-type tub either - the PVC-type plastic is notorious for static.
If you don’t have a real anti-static bag, just wrap it in aluminum foil.

Note that ESD (static) damage does NOT have to involve a visible spark. Also, the damage may not be noticeable right away. You can zap a MOS device, and it may work for a number of weeks, and then go bad for no apparent reason.

Meanwhile, slightly off-topic: Don’t store important documents, photos, etc., long-term in PVC containers. PVC and other vinyl-based plastics will ‘out-gas’ and damage stuff over a period of years. I know about this because my brother is an archivist (knows about the issues of safely storing documents long-term).


Sorry about the arrow (yes, that’s what it was, Andy; and, yes, it is a perfect indication of what my site will be like); I edited it so that it’s all pretty, now.


What I had tried to do was this trick with a really old version of AIM (I like using AOL 2.0; it makes me feel special) that makes a shnazzy arrow.
Oh well.

Jim, I’ll make you a deal.
You finish that waist rotate and put it up for sale, and I’ll buy it and the rest of the parts that I need so that I can build the bot (having the pieces tends to help, when one is building something).


Pete, thanks for the warning about the tupperWARE.
I wasn’t aWARE (yea, yea, bad pun, I know) that it’d ‘out-gas’ over time.
That shouldn’t be a problem, though, since they’ll only be in their tupperware for another two weeks.

The warning about the static electricity is a lesson already learned, though.
The underside of my desk (where my knees are always touching) is aluminum, I have an antistatic mat under that same desk, I keep the tupperware box on that mat, I always touch my chair (which has metal armrests) before I sit at my desk, and I live in the wetlands (Ever heard of the Jersey cranburry bogs? Right next door.), so the humidity never drops below 70%.
Between all that, I haven’t had any problems since I set it all up.
The learning of that lesson involved frying two brand-new, $400 a piece, 500MB RAM chips.

Needless to say, that won’t happen again.


But… you made me leery, again, so I’m going to crumple a bit of aluminum foil around the SSC-32…

Oh, btw, about the site:
I’m only going to be updating it after really key times (i.e. when I finish building it, first steps, established wireless communication, gave it a head, and that sort of thing).
Between college, working on the bot, and women (more expensive and time consuming than college and robotics, combined! :stuck_out_tongue:), I don’t have much free time.


Regarding ESD, you can have all the safe grounding and ESD equipment but that still will not protect ESD sensitive devices from static generating materials. At my work, we are required to take ESD training once a year.

Styrofoam cups are among some of the worst. Even pulling scotch tape of a spool can generate a large enough charge to cause damage. I keep all my stuff in Static Shielding bags (silver in color).

There are Anti-static bags (usually pink in color) but these bags can still allow ESD damage; because it does not shield the ESD from entering the bag.

Anti-static = Non static generating materials
Static Shielding = Shields ESD from penetrating the bag.

It’s very common in the electronics industry to have devices put in a pink bag and then put inside a silver static shielding bag.

As for the humidity, it’s a myth. It’s true humidity reduces static electricity, but does not eliminate the risk. Just because your clothes are not sticking to you, or the hair on your head is not standing on end, does not mean you are static free.

Just some more info to share with you.

Well, I guess I’ll put “grey bags” :wink: on my shopping list, then.

Thanks for the warning!

A couple of bucks in bags is well worth protecting a couple of months of work.


I don’t mean to drag this topic on but I thought some might be interested in what ESD damage looks like inside the delicate IC.

The photo below was taken with an electron microscope:

Forget the static bags… we all need electron microscopes!

The first of my biped’s parts arrived just now: the FSR’s.
I’ll post back later today and tell you guys how it went.

Now this is getting exciting… :laughing:


I got it working in just a couple minutes (read- three tries) without even frying anything!
Here’s a pic of my test circuit below:
(The white covering on the wires going to the SSC-32 are pieces of duct tape which I used to label them because I don’t have a memory :slight_smile:)

The only problems that I’m encountering is the seemingly low sensitivity of this circuit.
It’s very difficult to pinch one sensor lightly enough to give a reading of less than 255, yet still squeeze hard enough to get a reading above 0.

This will probably be too sensitive for my purposes.

I know that I will end up fixing the values eventually in my program, but I’d rather that I get it closer mechanically, first.

If I want to shift the thresholds to a higher amount of pressure, what would be the best way to do that?
I’m thinking that putting a resistor across each FSR, so that some of the current will be able to bleed off through them, thus allowing for higher pressure readings.

Will that work as I expect it to?
And, if so, does anyone have any suggestions as to what resistor value would be a good one to start with?
I’d use four pots to find out what would work best, but I don’t have four pots, although I do have a bunch of hanheld electronic games which are great for harvesting resistors from.


I see four wires coming out of what appears to be a lego brick and to FSRs. That leads me to believe that you are connecting them in some other way than was discussed in the “New Biped” thread. if you draw up the current connections, I can steer you towards an answer.

Believe it or not, that brick is a prototype carrier board for a set of small IC’s.

I set up the circuit exactly as the diagram in “new biped”.
Here’s a sketch of how it’s wired:

ok, then perhaps I see fewer FSRs than are really there… are there 2 or 4 on that board? If two, you have two fixed resistors on the other side of the dividers, what are the values? If 4, and they are configured opposed as in the diagram then the only reason I can think that you’d have sensitivity issues is if the resistance change may be non-linear near the low end, making the ratio appear to suddenly jump when pressing only on one. I’ll read through the docs tomorrow morning and see if that’s the case.

Also, be sure that your connections are solid. The pins on those are awfully thin for breadboards. If one of those FSRs is loose and disconnects, the value the ADC would see we be equal to the connected side. So if the resistor between 5 and the ADC is connected, but the one between ADC and 0 disconnects, the ADC will see 5. I ended up soldering on a couple PCB pins to the leads to get them to fit into the standard headers.

Hello Nick_R.
I found the FSRs you have chosen on the website you linked to awhile ago. They do not seem to have any real sort of data sheet available that would give force vs. ohms type of data. Lacking that it may be slightly more difficult to recommend values without some testing on your part. Have you run any tests where you measure the resistance of the FSR against some unit of measure? The unit of measure can be oz or grams of course but it can just as easily be anything stackable like pennies or nickels. Once you have a few points you can pick a resistor to scale the output voltage over the force range you are looking to accomplish. It may also be instructive to run this test for few sensors and plot the results together on the same graph. I am guessing, based on similar types of soft touch keypad designs, that you will not find them to be particularly linear or especially repeatable unless you very carefully control the contact areas of the sensor. Not suggesting it will not work for your application but rather just something to be aware of in your evaluation of them.

I do not know if you have any digital outputs available but if you do have you given any consideration to using a multiplexer on one or more of the analog inputs available to increase the number of inputs?


It seems they are roughly linear once you get away from the low end, put probably under more weight than you’re hoping to sense. As such, I’m not sure how nick_a pulled off using 2 of them in one divider and getting much meaningful data out of them unless his biped was quite heavy.

need to clean my flippin’ glasses I guess. :unamused:

Those are the same ones I’m planning to use for the SES tubing foot pressure sensor. Still waiting for my samples but it looks promissing. Here is an image of what I’m doing, although the Interlink one isn’t in the picture. The idea is to affix the sensor to the aluminum hub using it’s adhesive backing, then the adhesive backed rubber bumper goes on top of the sensor, then the rubber foot slides over the whole thing.