Let's Make Robots!

Sintra / expanded PVC

Hey all you users of expanded PVC:

I just got a nice big piece of sintra for my next project. Very cool stuff. Light, durable, and best of all, FREE!!! (got it from the showroom of a local plastic supply).

So before I go ahead and ruin it, let me throw out some questions to those who have used it:

1. What do you use to glue it? Super Glue? Plastic bond? Pipe glue?

2. What about cutting it? Jig-saw? Dremel?

3. Has anybody tried molding/bending/shaping it?

Crystal Oscillator

Hello to my fellow robojunkies!

I'm trying my hand at building my own circuit for my next project, and I've finally (I hope) picked up all the parts I need, but I've got a question. The part SAYS it's right, but it's so much bigger than the one on the project board.





Resistance and Ohm's law with Leds

Okay, this question is based on OddBot's great build your own ir sensor tutorial.

I noticed that the schematics showed a 150R resistor inline for the 2 IRs, but 82r for the single version.

My understanding of Ohm's law is that if I increase resistance, I decrease current. Therefore, wouldn't I want less resistance for the 2 leds?

Or am I missing an important part of the equation? Is the transistor increasing current, and so more resistance = more voltage?

the schematic:

Boosting speakers

Once again, I beseech the robot gods for some info ...

Speakers: How can I boost the sound/tune command from a picaxe to a speaker?

I've got a small 8ohm speaker that I've used in the past, and it works great (as long as the motors aren't droping the voltage) but  I want to boost my output. I've also got a much bigger 1 watt speaker I want to use. How would I boost it?

not sure what a pull-down resistor is ...

let the noob questions continue:

is this a pull-down resistor?


And if so:

-Is it just to keep a pin "low"?

-would i use it on any out pins as well?


combined analog input

Ahoy me hearties!

I'm working on a bot that will have a lot of sensor requirements. It must be able to sense objects both at the top and the bottom of the frame. Since I don't want to have to keep track of 8+ sensors, I was hoping to combine some of the sensor inputs.

For example, the bot will react the same to an object sensed at the bottom as one at the top, can I combine them?

Will this schematic work? And if so, will the adc reading be a sum of both sensors, or merely the highest one?


What jack do I use to program my 'axe?

Hey All,

Is this the jack that I need to connect my picaxe to my pc? The diescription doesn't say anything about connecting ...

I2C vs Serial

I hereby submit another plea to the robot gods out there:

I've read a lot of very informative info on both i2c and serial communication as a way for one IC to control others. My question is: which will work better for my needs?

My plan is to make a robot that has a seperate IC for each aspect of its behavior (movement, communication, etc.). So which is faster? cheaper? fewer wires? easier to program? I'm sure both have pros and cons.

Okay, go.

Op Amps - why/how?

Hi All,

I've been sniffing around the Picaxe forum for some tips/ideas, and I noticed that almost every project they have uses some sort of Op Amp.

Can anyone give me any pointers on using an Op Amp with a Picaxe?

Hacking a Pot

Hi All, it's time again for Calculon's noob question of the day!!!

For today's question, I'm hacking a sound recorder that has a "tweak" feautre on it. This tweak is a potentiometer that determines the pitch of the playback. What I would like to do is replace the physical turn-the-knob with PIC outputs, so my robot can do the tweeking itself. Is that possible?