Laser DeveloperRev1 is a stable test board for further software development. New features specifically for educational purposes have been added:
- Laser pulse width controls added.
- Laser power controls added.
- Updated laser CAD model to improve optical alignment.
- Made I2C pins available to the user.
- Increased mounting holes size for optical parts.
- Moved main supply to HVI to allow for battery operation.
- Added power controls on VGA through D2 PWM.
You will notice on the circuit board overlays that there are lots of small holes and very few visible tracks. The holes bridge the inner ground layers and outside layers together to reduce transmitted interference and cross talk between the laser driver and receiver circuits. The signal tracks are on the inner layers, shielded by ground plains, to reduce electromagnetic susceptibility.
Above is the top side of the board and below is the other side showing the pulsed laser diode (PLD) and the avalanche photodiode (APD). At the moment we're using a laser from Laser Components and an APD from Hamamatsu.
In order to test Unruly it's important to be able to access the components on both sides of the board while it is running. This is done by adding "wings" instead of headers. These wings are just headers soldered on at right angles.
The optics are then screwed on.
Using the wings, jumper cables connect the ItsyBitsy M4 Express to the Unruly LiDAR leaving the back of the circuit board accessible to an oscilloscope.
Test 1 - Unfiltered signal stability - indoors:
Results:
Single shot STDEV (standard deviation) = 1.0 cm (33 ps)
Single reading APD bias voltage measurement STDEV = 0.11 V
Single reading APD temperature measurement STDEV = 0.2 C
Discussions
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Please, can you say the the settings of the device at witch you get this results (Test 1 - indoors) - APD voltage, IC5 gain, comparator threshold level?
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There are quite a range of values that can be used. For this test I used:
APD voltage = 120V
VGA gain = 14dB,
Comparator threshold = 50mV.
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Thank you for the information.
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If it were just a few, what would the realistic cost price be?
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Retail selling price US$120. We're hoping to finish the design of Rev2 today - this version has a different chip set that should be cheaper to manufacture but may have slightly reduced range performance. We have commitment from LightWare.co.za that if we can get the retail price below US$100 then they will make in batches of 100 at a time. Also RobotShop.com has expressed interest in distributing Unruly. Some way still to go to a finished product because we need tooling for the optical holder (US$20k).
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Are you going to make these available to sell?
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We are hoping so. It really depends on how much interest there is from the public. Some of the components are quite expensive so it probably isn't worth making just a few. I'll post new information as I get it.
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