Plume – Receiver


Today, I have worked on the receiver. We have two options.
The first one is to use the solution used by the Razer Hydra, 3 different coils.

The other solution, that I have studied today is the solution used by the STEM System : 3 concentric coils.
This solution simplify the equations since the coils are truly concentric.
I have designed a 3D model that I  will print tomorrow.
Sans titre 3


Now we are working with Guénolé on the low noise amplifier.

Plume – Let’s prototype

Hi all,

I have started with Guénolé our first task : build an electrical prototype of the Plume.
First, we have selected the wire for the coils of the emitter. We plan to use a copper wire with a section of 0.08 mm².
I have estimated that at 5 meters we will have a magnetic field of 10^-10 T and a tension of 100 μV at the receiver coil.

Then we have studied the STEM System by Sixense. They leak some information about the product.
They use the same technology, a concentric 3-coil design.
They have a DSP that handles the processing of motion tracking position and orientation.
The device generates pulsed AC signals at frequencies of 30 kHz and it can works at 10^-7 T.
And the best for the end.

Now we are working on the receiver circuit. We have to amplifier and filter the signal.

Plume – Razer Hydra

Today, we have analysed the Razer Hydra a bit deeper.
Now, we know that the transmitter emits pulses in series, 3 pulses of 4ms long followed by a pause of 4ms.
This gives a refresh rate of 60Hz for the position.
For the coils, they use an alternative currant  around 18kHz.
And I have started to reverse engineer the receiver : schematic.

This analysis will help use realize our first working prototype.

Pictures :
IMG_1683 IMG_1685

Olivier, Benjamin

Plume – Magnetic Resonant Coupling

Looks like we have a winner.

Today, I started to study the Magnetic Resonant Coupling technology.
First with the schematic of the Razer Hydra.
For the receiver, they use a low noise Precision CMOS Amplifier and a multiplexer to choose one of the three coils.
For the transmitter, they also use a multiplexer and a LOW-VOLTAGE RAIL-TO-RAIL OUTPUT OPERATIONAL AMPLIFIERS but i still don’t know why.
Afterwards, I studied some scientific publications about the subject.

One of the solution to get the position and the orientation is to use the 3 transmitter axes and 3 receiver axes successively.
We will have 9 equations for 6 unknowns. We should be able to solve the system thanks to the following property.
The magnetic field of a typical coil is elongated along the coil axis so that the field strength depends not only on the
distance but also on where around the coil the receiver is placed.

But with this solution will we have to solve the following problems :
-How we will handle the synchronization between the transmitter and the receiver ?
-How we will solve the physics equations ?
-With the symmetry of the magnetic field we will only have the position in a 1/8 of space. We may need an accelerometer.
-We need a 5 meters range but the energy transmitted in the field decreases with 1/r^6 and the WHO (World Health Organization)  say that the magnetic field should be bellow 100 micro Tesla to be harmless.