Monthly Archives: October 2015

The final version of the DOLPi whitepaper is now available here: DOLPi_Polarimetric_Camera_D_Prutchi_2015_v5

Hack-a-Day just announced the finalists for the 2015 Prize, and DOLPi is one of them!  Hack-a-Day Prize 2015 Finalists for the announcement.

Here is the list of Finalists:

• DOLPi – RasPi Polarization Camera
• FarmBot – CNC Farming and Gardening
• Eye Controlled Wheelchair!
• Gas Sensor For Emergency Workers
• Household Electrically Enhanced Wet Scrubber
• Luka EV
• Portable environmental monitor
• Light Electric Utility Vehicle
• Vinduino, a wine grower’s water saving project
• OpenBionics Affordable Prosthetic Hands

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Although the circuit of shown so far as the liquid crystal panel’s AC driver works well, I’m not too happy with the intrinsic non-linearity of the FET.  Because of this, today I designed and tested an alternative, a bit more complex, but I believe more elegant design.  In the circuit shown above, the LCP drive amplitude tracks linearly with the DAC’s output.

The non-inverting amplifier built around U1 approximately doubles the output of the DAC. This voltage is then presented to an H-bridge implemented by the analog switches in U2. The H-bridge produces a continuous biphasic train at a frequency given by the oscillator built around U3A and U3B. U4 doubles the +5V coming from the Raspberry Pi to power U1 and U2. The LCP is connected between the legs of the H-bridge.

A new version of the DOLPi polarimetric camera whitepaper has been released at: DOLPi_Polarimetric_Camera_D_Prutchi_2015_v4