Related Articles

More

Related Categories

More

Recently Added

More

Solar Cells Construction

Amber Said:

BEAM bot construction?

We Answered:

3v solar cell is not going to work the same as a .55v solar cell for sure.

RadioShack is not a good place for your robotic project.
Solarbotics does. You can buy there anything you need for your BEAM bot. Solarbotics Internet store is easy to use and reliable.

http://www.solarbotics.com

Lewis Said:

Can anyone help me with some electronics?

We Answered:

A large area photo-diode is one with about 1 cm^2 area. They are often used for light measurement, and have a clearly defined area like 1cm^2 so it relates more directly to the measurement. Some I have seen have a built in filter so they have a photopic spectral response. Others may be enhanced in the blue region etc. The capacitance is like 100pF.

In a sense a solar panel is made up of larger area photo-diodes. I have used small solar cells for that exact reason, as well as commercial large area diodes. I have seen them used in various commercial instruments too. No doubt a purist could find arguments that the construction and doping are different. I would like to buy an argument on that sort of nit picking, but maybe the intention was explained somewhere in the course work and you missed it?

The reason I used large area photo-diodes was to simplify the optics. I had a LED with 5 degree beam as the source, and the entire beam fell on the cell, so needed no focusing at the detector end to maximise illumination. However they are not much good at low illumination levels and pulsed excitation, because of the capacitance.

The link below shows the differences from the amplifier point of view, and how to overcome some of the problems.

Because the larger ones can source a lot of current (more than the op-amp) I sometimes used them with a load of a few ohms (depending on the illumination and current so that there is about 10mV) and an instrumentation amplifier. This can be filtered easily so is less prone to interference (such as a radio transmitter) and can have a long cable with little impact, being balanced.

Discuss It!