Let's Make Robots!

Robot Sentry

This website may interest some of the more creative amongst us :)

Comes complete with DIY instructions.

Power toool motors - worth scavenging?

It's been a while since I spent any serious time at LMR, or indeed building robots. A pressing need to totoally renovate a Victorian house has taken priority so that I can generate enough money top pay the mortgage interest when rates rise again !

Sonar v. IR

I'm not clear how one should choose between Sonar and IR sensors. We seem to use either for detecting distance, but there must be operating characteristics that argue for one over another depending on circumstances.


Uses sound waves to determin distance

Doesn't detect curved or soft surfaces well



Uses light (infra-red) to determine distance

Doesn't work well in bright daylight

Some apparently opaque substances are not opaque to IR


What have I missed - there must be loads?

Happy Birthday

Tomorrow, 28 March 2009, it will be one year since GeekDad - a Wired Magazine blog - published an entry about Frits' Drum Machine, and so it will also be one year since, as a result of that article, I stumbled into LMR.

Thanks to Frits, Dan, OddBot, BOA, Rik, CtC, Cwignell, MycHolmes, Zanthess, Noise, maneuver, jklug, Nicola, Calculon, GroG, Ant and the dozens of others who make this an interesting place, extend my education, and generally put up with my nonsense.

Help: PicAxe 28X project board and Pulsin

Can anyone help me with this - I think I'm going mad ...

I have a PicAxe 28X project board and I'm trying to use it to read a high/low signal from another board. A high should be about 4.9v and the low about 0.1v.

I believe this is effectively identical to the SFR05 sonar. So I've taken Vcc (+5v) and Gnd from the PicAxe to my second board, and brought the signal from the second board back to the digital input pins of the PicAxe. My code loops using Pulsin trying to detect a rising edge. However, it never finds one. Here's the code:

Motion Detector

As my ignorance is almost complete, I'm looking for some advice on a suitable sensor to use with a PicAxe for a motion detector. I want to be able to detect a moving person at a distance of up to 2 to 3 meters, over a wide angle. Any ideas welcome - especially zany/arty ones.

How to implement a common ground

I have successfully transfered my SpeakJet module off the breadboard and onto some vero stripboard. I could power the SpeakJet module and the PicAxe module from one shared battery pack, but I'm wondering if it is possible to power each module separately with battery packs at different voltages (nominally, 4.5v for PicAxe and 6v for SpeakJet). The PicAxe communicates with the SpeakJet over a single wire. Do I simply need to connect the ground (0v) of each module together, or is there more to it than that?

I am Ratbert, hear me roar!

I'm beginning to really love my SpeakJet. Ratbert has found his voice (details here), and now you can hear him too. Roar is probably over-stating it. :)