Let's Make Robots!

TB-007 Metal Detector

TB-007 (ThunderBird 7) Big Brother of TB-6. (Blogged)

TB-007 is able to Detect Metal  (Coins, Rings, Gold, Electric Underground/Floor Cables and annoying Bottle Tops)

Improved Traction Design - aimed to cross over Stones and Sand.

I totally redesigned the Chassis of TB6 to make it more robust.

1st Video Shows it in Action. (-: towards the end are some Outakes :-)

2nd Video :- PolyMorph SkidSteer Helper ©



Here TB-007 has been fitted with a Wireless Camera -

so i can sit in my deck chair and watch its progress should it wander off.

The Camera is mounted to a servo which also has a Laser pointer attached (see main picture)  -

During "Fine Detect" phase of software loop, the servo positions itsself to look

and pinpoint with laser and Video the exact location of Metal Found.



The underside shows the layout of the Motors and a new PolyMorph SkidTurn Helper ©



Here is the  PolyMorph SkidTurn Helper © in more detail - In the Down Position.



 In the Up Position.

It is a hollow Poly-Morph "Thingy" which is connected to a servo - when activated it lifts the whole back end up into the air.

Then the front wheels can turn in opposite directions and the "Thingy" slides -

allowing TB-007 to turn effortlessly on the Spot - over the ground (polymorph is very smooth).



The BirdsNest (Thunder) ---- not so pretty but hey it works -

i have to install a second Voice Arduino so i have not finalised the layout

(-: velco straps are magic for rapid proto-typing :-)

TB-007 is Arduino Based with a Motor Shield (that controls the 2 main motors - 1 stepper motor and 3 Servos)



Here are TB-007s Test Coins -

The 5 Cent Silver American Indian coin known as the "Buffalo" is my Favorite.

The 500Lira (in video) and 10F (silver/bronze ringed) coins have the best detect signal.


The Metal Detect Electronics have be Hacked out of a Hand Held Metal Detector.


The Metal Detector consists of 2 separate detetor coils wound around a ferrite rod.

 The Circuit is a Beat Frequency Oscillator - able to detect metal and also live electrical cable.

  The Beat-frequency oscillator (BFO) is the simplest type of metal detector.

The basic beat-frequency metal detector employs two radio frequency oscillators which are tuned near the same frequency. The first is called the search oscillator and the other is called the reference oscillator.

The outputs of the two oscillators are fed into a mixer which produces a signal that contains the sum and difference frequency components. This signal is feed to a low-pass filter removing the harmonics. As long as the two oscillators are tuned to the same frequency, the output will have no signal.

When a metallic object disturbs the magnetic field of the search coil, the frequency of the search oscillator shifts slightly and the detector will produce a signal in the audio frequency range.




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After totally upgrading "ThunderBird 6"s chassis i decided that enough things had been altered to give TB-007 his own robot spot.

Web Cam has been Fitted along with a targeting Laser.

PolyMorph SkidTurn © device also installed -

If you have a robot that cannot turn on a carpet then this is a cool idea (see Video of it in action).

the PolyMorph SkidTurn © is great stuff A very nice idea, good job on that one!


...that's just insane! As always, great bot Gareth!

And i can't believe you have a 10F coin, those ones haven't been in use for about 8-9 years!


I have always collected coins  since "i was knee-high-to-a-grass-hopper" and now my son has caught the bug.

Each Coin has its own Metal Signature which i hope to program into the software.

By the way the double ring metal coins like the 10F (french) have a very strong wide signal. (so it may wander in your direction)

 I hope to check and graph my "test coins" shortly - here is an example of an English 50p coin.

Its pretty non-linear, so far - each coin (under test conditions) gives a different response.


And now all euro coins have those double metal ring so indeed your robot might leave your country...