Let's Make Robots!

SRF04 vs. SRF05

I used the SRF05 on a previous robot I built a while back and it was pretty impressive. It was also a little expensive. I just got a deal on a box of SRF04's and got them but I can't really find the main difference between the two models.

Can someone illuminate me?

Simplest electronic randomizer

I am trying to get some random element in the output of my latest solar powered bot. What I would like to be able to do is to have the bursts of activity from the solar engine make the motor turn one way or the other randomly. 

I tried creating a little circuit that had a comparator linked to two photosensors set close to each other so that it was mostly random what the output was but it got a little complicated and I figure that there must be a much simpler way to do that.

Best light bulb to test a solar circuit

I have been building a few solar powered dudes lately and I constantly run into the same problem. Since I mostly work on them at night I find myself in dire need of sunlight. My work bench is lit with a neon desk lamp and it is utterly useless to test any solar circuit. 

Can someone help me find the best possible artificial light source I could use to test my circuits?

LED trigger to picaxe signal

I found a new sound sampler module for my yellow drum machine. The problem I have right now is that the switch to operate and trigger the playback was a motion sensor. Essentially a LED in a thin tube.

I want to change that so that I can trigger that function from the Picaxe output.

Sound sampler board

Running a servo through a darlington

I am wondering what's the trick to running a servo (hxt900) on a picaxe28 (pic16f886) through a darlington transistor array.

I tried many different thing sbut the only thing that works is removing the darlington and replacing it with the 330 ohms resistor array (as specified in the "start here" recipe).

The only reason I am trying to do that is so that I can use the transistor array to work with speakers. 

Would it be a better Idea to just use the resistor array and then add transistors to each of the speaker's signal?

Some more unusual servo reactions in "start here" robot *FIXED*

I put together the "start here" robot and it worked perfectly, I then put together a chassis (foamcore, glue gun and thick wire), added a switch to turn it on/off and added a LED so it could communicate a few things and help debug. All this worked well but then I turned it on again and now the servo is acting completely erraticaly. In the "whichway" subroutine it now only looks left and then proceeds to move forward. Every time.