Category: quadcopter

We will continue our journey into building a quadcopter by working on the flight controller circuit.

The flight controller that we will be using is the Acro Naze32 Flight Controller ($31). This controller requires a little assembly prior to using because it comes in parts. The surface mount parts are on the board but the headers need to be soldered to the circuit. 

The board comes with a straight or angled connector. It is confusing which you want to use. If you get the board without the barometer module it is recommended to use the straight connector. If you get the board with the barometer chip then the angled connector is probably best so that you can put a GPS unit in the same space on top of the quadcopter.

In my opinion, the design of the board is counter intuitive and has some design flaws. The kit comes with three connectors that need to be soldered onto the board. The two headers that go through holes on the board are relatively easy even though one of the connectors is millimeters from a surface mount component. What makes no sense to me is the gold connector that you have to side mount pins to. A connection like this typically is easy to mess up and break under vibration. Why put an edge connector here and not put through holes to solder? The pin towards the middle of the board is close to three surface mount components. Overall, I think that the design is somewhat silly. Why ship extra headers at extra cost but skimp on board size and not put through holes for higher reliability? The connector that I am openly ranting about is the connector shown on the far left on the picture below (connected to pins 4,5,6,7, and 8).

The next step is to lock down all of the screws mounting the arms to the Q450. This is relatively simple and requires a 2.0mm allen wrench.  Once these are locked down we screw the prop mounts onto the motor with a 2.3mm allen wrench. The two photos below show the screws going into the motor then the prop spacer and nut to hold the prop.

The next step is to mount the flight controller to the quadcopter assembly. The assembly has an arrow on top pointing to the direction of travel. The circuit board also has an arrow pointing to the direction of travel. We are going to mount the flight controller board on top of the quadcopter using double sided tape (we could use screws and spacers if desired because the holes are on the board and on the quadcopter). If you use screws and spacers you need grommets to reduce vibration. The double sided tape tends to dampen vibration and keep the system from changing during flight. It is CRITICAL that you use enough tape to isolate the electrical components and the board. It is also CRITICAL that the arrows align with each other. This keeps the software and remote controller aligned. Moving the board off axis will cause imbalance in the motor controller and flight controls.

Once we have the flight controller mounted, we can mount the battery between the two layers. This is done with a velcro strap to allow for quick release. We loop the strap through the two rectangular holes on the bottom board.

The next step is a little difficult. We need to take the middle wire (red wire) from the 3 pin connector coming off the speed controller and pull it out. We don’t want all four speed controllers providing power to the flight controller. We take the middle pin out from three of our speed controllers and cover them with shrink fit tubing. The reason why we use heat shrink rather than cutting the wire is to have redundant systems to use in the future. We can always take the tubing off and put the cable back into the connector.

Now that we have three of the connectors modified, we can plug these connectors into the flight controller.

In the class we took a diversion and downloaded the baseflight-configurator using Google Chrome Store. This is done by searching for baseflight-configurator and installing the plug-in. Once the plug-in is installed, launch it and install the USB driver for the computer that you are using. Once this is installed you should be able to connect to the flight controller from a USB to mini-USB connector.

With this we have a connection to the flight controller from our laptop. If you click on the connect with the port configured to be at 115200 speed you should get a green Disconnect button rather than a red Connect button. As you move the quadcopter around you should see the motion mirrored on the laptop.

The first thing that we need to do once we have the baseflight-configurator running, we need to update the firmware and flash it to the controller. We download the firmware from github then flash it to the controller.

From this we go into the configurator and setup things like motor rotation direction, throttle max and mins. Make sure all features are turned off. We then save and it updates the flight controller firmware.

The class instructions starting at page 113 have screen shots of all of these configurations along with explanation of all options and selections.

One side discussion was that a mobius 1080p camera ($82) is a good add on. It allows you to record a flight and does not add much weight to the quadcopter.

Once we have the software operational, we can connect the speed controllers (and thus the motors) to the flight controller. Looking at the configuration diagram for a Quad X configuration we notice that the bottom right motor is channel 1, top right is channel 2, bottom left is channel 3, and the top left is channel 4. This corresponds to the pin block at the front of the flight controller (front being where the arrow is pointing). The numbering starts from the right side with pin 1 and goes to pin 6 at the left. The orange cable is the signal, the red pin (only connected via channel 2) is power, and the brown wires are ground. You can verify this by looking next to pins 6 and see the “-“, “+”, and square wave on the circuit board. In the photo below we have the speed controllers plugged into channels 1, 2, 3, and 4 with channels 5 and 6 unconnected.

 

The next step is to plug back into the laptop and test the rotation direction of the motors. By going into the motor testing tab we can energize the motors and rotate them at different speeds. This allows us to test the direction of the motor rotation and reverse the red and yellow wires going to the motor to have them rotate in the direction that we want.

The cool thing at this point is that we have a working quadcopter. We have a battery pack that is communicating to the flight controller. The flight controllers are pushing power to the speed controllers thus turning the motors. The only thing that we are missing is the rc controller to control motor speed and flight. We are using the laptop as the rc controller for calibration.

The next step in the class is to get your rc transmitter paired with the on-board receiver. Given that we had a Spektrum transmitter and receiver, it was different from everyone else. For ours we had to follow the directions in the Spektrum manual. Page 10 shows how to bind the receiver with the transmitter. We used the bind plug method (Binding Using the Receiver and Receiver Battery). We plugged the bind plug into the bind section of the receiver and unplugged connector 2 from the flight controller and plugged it into the receiver. We put the transmitter into bind mode and waited for it to sync with the receiver. Once this one done, the transmitter acknowledged the connection and we could power down the receiver.

The receiver has labels on the connectors. Looking from the bottom with the printing on the left, the bottom row is the bind/dat row. The next row is labeled Thro which correlated to channel 1. The Aile (aileron) is channel 2. The ELEV is channel 3. The RUDD is channel 4. The GEAR is channel 5. The AUX1 is channel 6. Once we map these to the receiver, we need to program the transmitter appropriately.

With the receiver connected, we power on the quadcopter by plugging in the battery (while connected to the laptop) and can calibrate the rc transmitter so that the controls min out at 1000 and max out at 2000. This is done for the four channels that represent thrust (THRO), pitch (elev), roll (aile), and yaw(rudd). By moving the controls on the transmitter we can see the controls change on the computer. The motors should also spin while you are playing with the controls. You should be able to verify the different motors spinning as you adjust the controls.

At this point we have a transmitter that communicates to the receiver. We have a receiver that is communicating to the flight controller. We also have a flight controller that is energizing the speed controllers and making the motors spin. The only thing that we are missing is a cover to protect our electronics and propellers.

The cover that we are using is a cover printed by the instructor. The cover is ABS so it is easy to modify with drill holes and cut excess edges off. You can then tape or velcro the top to the quadcopter frame. The instructor puts his receiver taped to the top cover. We are going to put our receiver between the two decks with double sided tape attached to the bottom. You can operate without a cover but your electronics are exposed and hitting the ground could get moisture or dirt into your circuit board.

We will use a dremel tool to route out parts of the cover to allow it to fit on top of the assembly and fix it to the frame using velcro.

The props are put onto the motor shafts. The rings under the quadcopter are stabilizers for the propellers to keep them from vibrating. The ring goes onto the shaft first followed by the propeller then the metal washer and metal nut. The metal washer is a bridge to protect the plastic propeller and help keep the nut tight on the shaft. Use a wrench to tighten down the nuts before flying every time that you fly. During flight, half the nuts are trying to get tighter and the other half is trying to get looser.

 

With this we have flight! Plugging in the battery and powering on the transmitter allows us to fly our new quadcopter!

Now that we are at the end of the class, let’s review the overall cost. The class itself was $345. This cost covered about half of the cost of building a quadcopter. The overall cost to build this system from scratch is just over $700.

The up front costs for this class are:

• $300 – rc controller
• $43 – Lectron Pro 11.1 volt Lithium Ion Battery
• $45 – Prophet Sport Li-Pro 35W Peak Battery Charger
• $345 – class fee

total cost: $733

Included in the ($345) class you get

• $4 – clear electrical tape
• $2 – solder
• $18 – apc composite 9×4.5 MR (2) and MPR (2) props
• $6 – XT60 connectors
• $13 – Diatone Innovations Q450 V3 quadcopter frame
• $21 – Afro ESC 20A speed controller (4)
• $3 – zip ties / velcro / double sided tape
• $13 – non-adhesive shelf liner
• $220 – Multistar 2213-980 14-pole outrunner motor (4 at $55 each)

total in parts: $300 that comes with the class

optional components are:

• $20 – prop balancer
• $8 – lipo battery monitor
• $60 – watt meter

Overall, this was a very good class. It was good talking about the theory and practical ways of building a quadcopter. The class does not focus on flying but does talk about when, where, and how to fly. You are on your own to learn how to fly and repair the quadcopter as you crash while learning.

 

In the last post we started by documenting a class that details how to build a quadcopter.

 

In this post we will look at the Diatone Innovations Q450 V3 platform ($13).

The first step is to solder the power connector with the female connector to the board. We solder the red lead to the “+” and the black lead to the “-“. We also put some solder on the pads that will be used for the motor controllers. On the Q450 that we got there are eight pairs of connectors. We prepared the outer four “+” and “-” pads with solder to accept the motor connections.

The next step is to attach the speed controller circuit (ESC) to the extension arm and solder the non motor connection leads to the board. The ESC is attached to the extension arm using zip ties. Nothing else needs to be done to attach it since it should stay in place and not slip during flight.

The ESC that we are using is the Afro ESC 20A ($21 each and we need four of them). The system has three types of connectors. One goes to power, one goes to the electronics, and one goes to the motor. In the picture below the red, yellow, black go to the motor. The black and red on the right are the power connections that we will solder to the Q450 board. The purple, red, yellow ribbon cable is the control cable that will be attached to the controller.

 

We use a simple zip tie and a non-adhesive shelf liner (part of $13) to keep the ESC in place as shown in the photo. We then cut the power cables (right red and black cables in photo above) and solder them to the Q450 board (shown below).

Once we have the power cords soldered to the Q450 board we screw the arm onto the Q450 to relieve the cable strain on the newly soldered wires. The connection should look like the photo below.

The biggest difficulty that we had was the spacing between the mounting hole for the arm and the angle that the cables came in. At times the black wire covered the screw hole and we had to re-solder the wire to attach from a different angle.

Once we have the arms installed, the next step is to mount the motors and test the electrical. We are using the Multistar 2213-980 14-pole outrunner motor ($55 each, we need 4).

Each motor is attached to the arm with four screws. When we initially tried fitting the screws through the arm a couple of them did not want to go through. The arms are injection molded and had a little “overhang” on the screw hole. Using an allen wrench we were able to clear the excess plastic and mount the motors on the arm.

 

 

Everything technical needs a diversion. This will be a log of building a quadcopter based on a class that I attended this weekend. The class is hosted by the Houston Hackerspace TxRxLabs. It is a two day class that results in a working quadcopter at the end of the class.

“Everything you need to know to start building your own multicopters. This is a hands-on class in which, by the end of the class, you will have built your own RC quadcopter.”

The pre-notes for the class can be found here. The most important thing to bring is a remote control unit similar to what is used for RC cars, boats, and planes. We purchased the Spektrum DX6 ($200-$300) from a local hobby shop in Houston. The majority of the class purchased the Taranis FrSky X9D ($300). The major benefit of the Taranis is that it is a 16-channel system rather than a 6-channel system for about the same price.

The instructor presentation is a good overview of the class.

The class started out with a discussion on where it is appropriate and not appropriate to fly drones. The best place to start flying is to fly on private property, local parks, or a certified flying field. There are places where you should not fly. www.airmap.io is a list of no fly zones. A good rule of thumb is nothing within 5 miles of an airport or over anything government facilities (state and local).
Also keep in mind where you are flying and what would happen if you loose power. For example, don’t fly over a highway or places with large crowds. The quadcopter has weight and can travel upto 50 plus miles per hour.

www.meetup.com/sotexdug is a local drone flying club. www.rchouston.com is another local flying club but not specific to quadcopters. They rate and list local flying fields.

 One important thing to focus on is making sure that your propeller is not too heavy on one side. This will cause stress and instability and excess wear and tear on your motor. A prop balancer is a good investment ($20). Cheaper balancers are also available and can be used by hand ($6). It is important to get something that will work with a 9 inch prop. The props that we are using for this class are APC Composite 9×4.5 MRP props ($9 for two props).

To balance the prop you mount the prop on the balancer and watch which side drops to the floor. You can add weight to the top part of the prop using small clips of clear electrical tape ($4). 

In this example it took 3-4 small pieces of tape to get the prop to remain relatively level. It is important that the tape not get too close to the leading or trailing edge of the prop. The tape should also be placed on the inside edge of the prop and not on the outside edge. The inside edge is the edge where the air flow is at a minimum. This changes based on how you mount the prop on the motor and rotation direction of the prop. The tape is relatively strong and should stick.

The next discussion was around battery life, best practices, and recommendations. Try not to discharge the cell below 3 volts and don’t store them uncharged. Charge them before you put them away for the week. They will loose charge sitting in the bag and if you get below the minimum charge it will not retain as much charge in the future. We purchased the Lectron Pro 11.1 volt Lithium Ion Battery (2200mAh ($69 for three pack) and 3500mAh ($43 for one) batteries). You only need one but we got two so that we could extend the flight time.

A good tool to have is a lipo battery monitor that shows the quality of your battery ($8 for a pair). A good rule of thumb is to store the batteries in a cool location. An ammo can is a good place to store the batteries because bad batteries tend to do bad things (fire, explode, insert what you want here).

You will also need charger that is compatible with the battery that you purchase. We selected the Prophet Sport Li-Pro 35W Peak Li-Po Battery Charger ($30-$45). The charger has a 2S and 3S plug on the front. We will use the 3S connector because the batteries that we purchased are 3 cell batteries.

 Servos are something worth looking into. If you are going to mount a camera onto your quadcopter to help with navigation you will need to tilt your camera up when you go faster and level when you slow down. If you don’t tilt your camera it will be pointing into the ground and not in the direction of flight. Most servos operate at 4-6V DC. For a nav camera a small motor with a separate battery might be better. You don’t want to loose your vision or have vision draw too much current from the rotors.

The speed controller is what controls the rotation of the motors. They are driven by a pulse width modulation (PWM) signal from the remote controller. They work on 5V and typically draw 500mA but do generate a significant amount of heat if used over a long period of time.

When selecting a motor it is important to know the prop characteristics, the current draw, the rotational speed at nominal operations. There are a variety of motors that you can select as well as a variety of props. You can look at the wattage and current that is being consumed. A watt meter ($60) is a good tool to have to fine tune the prop and motor relationship. It is not necessary but good to have when designing a quadcopter.

When looking at a prop, it is important to make sure that all props are the same. Don’t mix and match props on the same quadcopter. When looking at a prop it has lettering and numbering on one side, a smaller hole and a bigger hole. The bigger hole faces the motor and the smaller hole with lettering is the outer edge of the prop. The numbers on the prop designate the size and pitch. In our case we have two 9×4.5 MR and two 9×4.5 MRP props. This is a 9 inch prop when measured from tip to tip. The 4.5 is the pitch of the prop. This combination designates the lifting power of the motor-prop combination. The P designation is for pusher and the non P designation is for pulling.

If you are designing your own new system a good rule of thumb is that the quadcopter should hover level at half throttle. Many prop manufacturers have charts that show thrust in grams with rotational speed and amps/wattage for different motor-prop combinations. You can hook up a rig with a kitchen scale to measure force as well as current draw when looking at changing the motor and prop selection.

We will be using the Acro Naze32 Flight controller board ($30) for this class. You can get an upgraded board with barometer and compass ($40) integrated to measure elevation and direction. You can hook up a GPS to this system as well to get absolute position and fly waypoints. The PWM channel decoder integrates to the RC Receiver (and transmitter) and translates the controls into PWM outputs that go to the speed controller for the motors. The Naze32 is designed to work with six motors but we will be using four in the class.

 The first step in assembly is to prepare connectors for the batteries. We will be using the XT60 connector ($6 for five pairs) to bridge between the battery and controller. We use heat shrink tubing on the connector to keep from shorting while we are soldering. The resultant female side should look like the photo below.

 

Make sure that you put the red into the “+” connector and the black into “-” to ensure polarity.

 The next step is to cut the old connector from the battery and put the XT60 male connector on the battery. Make sure that you cut one, and only one, side at a time. Cutting both leads will short out the battery and ruin your day as well as the cutters and battery. In the photos below we cut the red wire, soldered the new connector on, and applied the heat shrink tubing. This needs to be done to make sure that the soldering iron does not short out the negative lead while we are attaching the black wire.

 

At this point we have a battery with the XT60 male connector and a wire with an XT60 female connector.