Introduction
This blog continues from Part 1 of the WiFi-controlled rocket launcher. In this short post, load testing was performed on the igniter's power supply and the output drivers.
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| WiFi Rocket Launcher Blank PCB |
Power Supply
The DC-DC converter, Texas Instruments part LMR50410, was tested for switch ON voltage threshold and response. Since the converter powers an ESP module and output drivers for the igniter, the load current test was set for 300 mA.
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| Power Supply Portion of Rocket Launcher |
An external power supply was connected to the launcher board. The voltage was increased in increments of 100 mV until the converter activated. For this board, the threshold was 4.1 V. The output switch ON waveform is shown below.
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| Rocket Launcher Power Supply Supply Turn ON |
A resistive load resulting in 330 mA was connected to the 3.3 V supply for testing. The output voltage dropped from 3.3 V to 3.28 V when the load was connected.
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| Rocket Launcher Power Supply Supply Transient Response |
The transient response for the power supply was measured for a 50 % load change. Captured in the image above is the response showing a recovery time of less than 200 ns for the supply voltage to settle back to 50 mV.
Output Drivers
The output driver circuit design had been established from the previous version of the launcher circuit board, which meant the operation was already known.
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| Rocket Launcher Output Driver Load Testing |
To test the output drivers on this board, a 5 Ω resistive load was used. The two output drivers were powered with 12 V to simulate the primary power source. Using the 3.3 V from the converter, the two drivers were activated.
V(supply) = 11.92 at drivers no load, V(supply) reduced 11.79 V with approximately 2.3 A load current because of cable losses.
Measurements were taken with 2.3 A of load current
V(load) = 11.19 V
V(diode) = 401 mV
V(high side driver) = 102 mV
V(low end driver) = 124 mV
In part 3, the code for the rocket launcher will be started in Arduino IDE.
