In flight current meter / logger for RC aircraft

In flight current and temperature logger for radio controlled models. Allows electric power setup to be tuned using inflight measurements rather than ground based testing. The core is an Arduino nano that I had lying around. The current sensor is a zero to 30A ACS715 hall effect device on a breakout board ready assembled. The temperature sensor is a TMP102 ready assemble on a breakout board, it uses an I2C interface. These devices are just wired to the Arduino and it is ready to go.

Once complete motor current and battery temperature can be monitored in flight.

For more info go to http://myweb.tiscali.co.uk/assocofbodgeartists/Articles/InFlightMeter/InFlightMeter.html.

Low cost modifications to Parkzone micro Sukhoi for better aerobatics

The Parkzone micro Sukhoi is a lovely aeroplane. With full 4 channel control it is capable of all classic aerobatics. However out of the box it lacks the thrust and control response for good aerobatic performance. It has poor vertical performance looses too much speed in loop and Immelmans to make it cleanly over the top. So a few mods are in order.

Mod 1: Get the CoG further back

To achieve this without the addition of weight the main RX board with its elevator and rudder servos needs to be moved back from its original position behind the motor. So cut the decals to remove the top cover. Remove the push rods for rudder and elevator. Unplug motor and aileron servo. Carefully remove the RX board by cutting away the foam. Carefully remove most of the remains of foam and glue from the RX board, just enough to ensure the board sits flat and no excess glue sticks out the sides. Using double sided tape mount the RX board to the rear section of the wing as shown in the picture above. Make a hole in the rear of the battery bay for the battery plug to pass through. Extend the motor wires and plug motor and aileron servo back into the RX board. Cut the push rods shorter as required. Remove Z bent wire from discarded ends and fit to end of short push rods with very small bore heat shrink. Offer up push rods adjust position of Z bent wires for best fit and wick a little thin cyano under the heat shrink. Refit push rods, use second hole out from hinge on surface control horn and 30 to 50% exponential on rudder and elevator for good aerobatic response. Test controls for full and free movement, bend wire loop and rear end of push rods as required ensuring controls are central when TX sticks are central. Re-attach cover with some clear fablon patches.

Mod 2: Change the Prop

The original prop just doesn't seem right, it's either under loading the motor or overloading it I can't quite work out which. However a 5 inch diameter 4.5 inch pitch GWS slow fly style prop seems ideal, cheap and light. To mount the prop I drilled down the middle of a nylon screw so that it would self tap onto the gearbox shaft thus providing a prop shaft to mount the prop. However gluing a piece of plastic tube into the hub which could then be screwed onto the shaft would be a little lighter.

With these mods implemented flight was superb with smooth and easy loops and rolls.

Making tin fuel tanks for model aircraft

A tutorial on making tin plate fuel tanks for model aircraft has been added to the InfraCortex website.

http://myweb.tiscali.co.uk/assocofbodgeartists/Articles/tintank/tintank.html

Swing between two posts

As with most families in the UK we have a relatively small garden. But of course we want to provide fun toys in the garden for the kids to play on.

Initially I am installing a set of removable posts so the garden can be configured for different purposes. One of my first problems was how to rig a swing between 2 posts ~4m apart. The solution is a trianglated rope swing.

The top rope forms two triangles providing support points at approximately the width of the seat, thus the seat can be made stable with respect to side to side motion. Snap shackles are used to clip the swing to eye bolts in the posts. This makes the swing easily removed. One extra snap shackle is used to join the ends of the top rope in the middle. The swing seat is supported conventionally below the top rope triangles. The posts need support bases that extend 2feet or more below ground as they have to act as canteliver supports.

Simple RC Speed Controller

My daughters model boat required a speed controller with forward and reverse control. Over a couple of evenings this simple speed controller for brushed motors was developed.

It uses a 6 transistor H-bridge drive. Two PNP power transistors are used for the source side of the H-bridge and two NPN power transistors of complimentary characteristics are used for the sink side of the H-bridge. The bases of each sink-source pair are connected by a small NPN transistor. This allows just two lines to control the H-bridge drive. This allows forward, reverse and off control of the motor. Braking cannot be acheived with this type of H-bridge. Bipolar transistors are used because the efficiency required for this controller is low.

The H-bridge is controlled by a small micro-controller, PIC12F675. It utilises its external interupt pin to monitor a standard PWM RC servo control signal to control the duty cycle and direction of the H-bridge. The motor is driven by forcing one one of its inputs high, the input is also PWM with 206 levels of duty cycle. Thus direction and speed of motor is controlled.

Circuit schematic, PCB layout and PIC code are available free at www.infracortex.com. Also it is intended that this controller with be developed into a speed controller with current and rpm feedback so keep upto date with events here.