Model Rocket Motor Dynamometer (Arduino Uno)
Introduction: Model Rocket Motor Dynamometer (Arduino Uno)
Hi. My normal YouTube "job" has been chasing and shutting down scammers. I've taken a break from that and have recently been playing around with model rockets, drones and airplanes.
Making model rocket motors is fun but when it gets serious it becomes necessary to measure the motor's performance so that the effect of fine adjustments can be visualised.
This project uses parts available from Amazon (and many other retailers) and there's nothing complicated apart from the code, which of course is downloadable from this instructable later.
There are several modules in the project:
1.Strain Gauge Load Cell
2.Motor Mounting Platform
3.Audio and Visual Warnings
4.Motor Ignition Relay
5.Control System
6.Data Retrieval and Storage
The whole system is designed to be stand-alone - requiring no PCs/Laptops to acquire the motor data. Once stored on SD card, the data can be safely removed from the system and read by a PC etc to generate graphs / charts.
Supplies
Supplies
Note: All the items listed below are from Amazon. The number in parentheses (Amazon B081JNXBSZ) for example, is Amazon's universal item number for that part. There are many other places to buy the components, mostly competitively priced. This list is what I used to make the project myself.
1 x Load Cell With Amplifier - DollaTek 10kg Small Scale Load Cell Weighing Pressure Sensor With A/D HX711AD Adapter (Amazon B081JNXBSZ)
1 x Arduino LCD Shield - KEYESTUDIO LCD Shield Module Display 16x2 Display Module Blue Keypad Shield for Arduino R3 Mega2560 (Amazon B07H3Q3X6C)
1 x Arduino Relay Module - ICQUANZX 5PCS KY-019 5V One Channel Relay Module Board Shield For PIC AVR DSP ARM for arduino Relay (Amazon B07BVXT1ZK)
1 x Arduino Uno (compatible) - ELEGOO UNO R3 Board ATmega328P ATMEGA16U2 with USB Cable Compatible with Arduino IDE Projects RoHS Compliant (Amazon B01EWOE0UU)
1 x SD Card Module - Pxyelec 1pcs Micro SD Card Micro SDHC Mini TF Card Adapter Reader Module For Arduino (Amazon B07F9LT72N)
1 x PP3 Battery Clip - 5Pack 9V Battery Snap Connector 9 Volt Battery Clips Connector Buckle Plastic Housing, T-type (Amazon B07HD3PBDT)
1 x Pushbutton - SPST Red Momentary Push Button Switch 1 Circuit 1A 250V off-on (Amazon B082VFKJMF)
Various Connection Wires, Heat Shrink, Solder etc.
Case of some sort
Step 1: Strain Gauge
The strain gauge recommended consists of a bar with some holes drilled in its side. On top and below the holes are some components glued on with epoxy. These components are strain gauge elements. When the bar is pressed at one end, the metal above the hole is stretched. The metal below the hole is squeezed. The elements measure this minute movement by means of a flexible, resistive PCB. As the PCB is stretched the resistance increases. 769
Squeezing the PCB reduces the resistance. Between the Strain Gauge and the Arduino is a processing amplifier which takes the minute resistance changes and converts them into meaningful, readable values.
The Strain Gauge amplifier has 6 connections at one end and only 4 at the other. We are going to use the 4 pin connector - Gnd, Vcc, Data and Clock to join the amplifier to the Arduino. The connection of these pins is shown in the overall wiring diagram. There are 4 wires coming from the Strain Gauge itself, Red, Black, White and Green. They are connected as follows : Red to E+, Black to E-, White to A- and Green to A+
There is a small modification to do to the strain gauge amplifier board. Originally the sampling rate is 8 per second, which is not good enough for our purposes. If you look at the picture of the board you will see a large component calle U7. At the top right of U7 is a power supply pin (pin 16). The pin below it is the sample rate pin (pin 15). What is needed is to carefully apply heat from a soldering iron to pin 15 and lift it up from the PCB a tiny amount. The carefully bend the pin towards pin 16 so they overlap a little. The just quickly solder pin 15 to the top of pin 16.
Don't worry, this sounds much harder than it is. 611