VN-300 Harness

This is a follow-up for implementing the VN-300 in the 2023 system architecture document. The discussion was originally between using the PDB or the Pixhawk to power the VN-300. This document sheds light on the difference between the two implementations.

Math

Not including antennas, the VN-300 has a maximum power draw of 1.25 [W]. The antennas use an external power supply coming from a PDB. Each antenna has a maximum current draw of 12 [mA], which gives the power consumption of the antennas to be 2 * (12 * 12) = 0.288 [W]. Factoring this in, we have a maximum power draw of the VN-300 to be 1.25 + 0.288 = 1.538[W]. Given that we are looking for an upper bound on the current and the switching regulator on the PDB is not perfect, we assume that the regulator is 90% efficient. This results in the value of our max power needing to be multiplied by 1.1 to compensate for non-perfect conversion. Using P = IV, we have I = (1.538 * 1.1) / (12) = 141 [mA] (rounded up). The maximum current is 141 [mA] at 12 [V]. Another option is using the Pixhawk to power the VN-300. The Pixhawk outputs 5 [V}, so using the above method, we get a maximum current draw to be 302 [mA] at 5 [V].

Diagrams

With PDB

Using Pixhawk

Crimping the Contact

Given the crimping tool is $700, we had to find alternatives. One such alternative was stripping the end of the wire to be placed in the contact, and using a crimping tool to crimp the contact and the wire. To get an even crimp around the wire so the contact fits in the connector, move the crimper around the connector until it fits the form of the wire and can be inserted into the connector with a little force. For lack of a better term, the “pry tool” is best for applying a bit of pressure to get the contact in the connector, as it is pretty awkward trying to use fingers.

Useful Resources

Crimping connectors Crimping & Assembly Guide ǀ Datamate high-reliability connectors