In order to be able to connect the USB port to a Computer we need to disconnect the voltage feed from the USB cable. However in this project it is powered from a LM7805 voltage regulator (U4). Note: Normally the Teensy 3.1/3.2 is power fed via the USB port. On eBay, use the search criteria: “Nema 17 1.7A 2 phase 4-wire 4.2kg.cm” This motor does over 300 RPM quite nicely when adjusted for a current of 1.4A. Having a much lower phase coil impedance, it is also capable of quite high speeds before losing torque.
This stepper motor will not go very fast before losing torque, 100 RPM is probably the highest usable speed. Needed, there is no need for end stop switches. By limiting the torque of the motor to the bare minimum The capacitors (see antenna descriptions further down the page). Using this stepper motor, only about 250mA per phase is requ ired to reliably turn
Using three different vacuum variable capacitors, generally I have found that when Having built 3 magnetic loop antennas thus far, Use the search criteria: “Nema 17 Stepper 2800g/cm 0.4A” or These Stepper Motors cost approximately $20 including shipping if 30 ohms per phase, each phase specified at 0.4A max.I have used several types of Nema-17 format two-phase Stepper Motors, here are a couple that work well with the controller: This current limitation feature can also be used to adjust for the minimum torque necessary to reliably turn the capacitor - thus ensuring no damage if we accidentally try to go beyond the end stops. In other words, the Stepper Motor controller circuit provides accurate current limitation. Microstepping is achieved by providing current to both phases at the same time, but in different proportions for each microstep. The stepper controller circuit used in this project is capable of driving up to 1.5A per phase. Need at least 5 to 1 gear reduction for to get sufficient resolution If you are using aīutterfly or similar air variable capacitor, then you will probably Tune a multi turn vacuum variable capacitor. This is more than sufficient resolution to Pair with an accuracy of 1600th of a revolution, over a range of Other words, the Controller can keep track of a frequency/position
#Google tuner full#
Motor will give 1600 distinct positions per each full revolution. Typical Stepper Motor gives a resolution of 1.8 degrees per step.Įach step can be divided into 8 microsteps, hence a 1.8 deg/step
#Google tuner serial#
This quickly becomes very frustrating, especially if you, like me, like In other words, the antenna has a very narrow bandwidth, if you move byĪ few kHz then you need to retune the antenna. Of a wavelength or more then the antenna would more accurately be characterized as anĮlectrical loop antenna, with characteristics similar to those of a dipole.Įfficient Magnetic Loop Antenna has a very high Q. If the inductor circumference approaches ¼ Wavelength, then the efficiency of the antenna will suffer. The inductor has a circumference of much less than, say, 1/10 th of a Magnetic Loop Antenna is basically just a resonant circuit using an oversized inductor and an adjustable capacitor.
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