Summary of Contents for Eggtimer Rocketry Eggtimer
- Page 1 Eggtimer Flight Computer User’s Manual Release 1.48b Board RevC © 2013 Eggtimer Rocketry All Rights Reserved - 1 -...
- Page 2 Eggtimer Features Altimeter rated to 29,500 ft ASL, resolution to approx 1 ft. Logs data for last 32 flights, “beeps” out maximum altitude of last flight Flight data can be downloaded to a computer using USB interface cable (included) to .CSV format, for...
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Page 3: Limited Warranty
Limited Warranty Eggtimer Rocketry warrants that all of the parts on the packing list of the Eggtimer kit have been included, and that they are all in working condition. If you are missing something, contact us immediately at support@EggtimerRocketry.com... - Page 4 How to Use the Pre-Programmed Flight Settings…..27 How to Download Flight Info…..34 How to Test Deployment Charges…46 How to Set Up the Eggtimer for Multiple Deployments…..47 How to Set Up the Eggtimer for Airstarts…50 How to Use Servos with the Eggtimer……..41 (#10) Wire Options for your Eggtimer……….13...
- Page 5 A General Introduction to Flight Computers A flight computer is used to record the flight path of a rocket, and to optionally deploy recovery devices. Typically, you can use it to find out the maximum altitude (apogee) of your rocket, the maximum velocity of the rocket, the maximum acceleration (G forces) on your rocket, and other flight characteristics.
- Page 6 Launch Detect Altitude. Since most of the motors that the Eggtimer is designed to be used with come with built-in ejection charges, the Main deployment channel can be used for the main...
- Page 7 BEFORE you install it in a rocket, and certainly before you try flying it. Battery (3V) – Two solder pads, marked “+” and “-“, for connecting the Eggtimer battery. Typical draw is about 8 ma when running, recommended battery voltage is 3v-4v. DO NOT...
- Page 8 Quest G2Q2, or 9-12v alkaline batteries for #36 nichrome wire or other igniters. The Eggtimer is capable of handling up to 60V/8A up to 65W, so you can ignite even an Aerotech Copperhead igniter with it, assuming you have a strong enough battery (i.e.
- Page 9 Data Port – 6-pin FTDI-compatible standard header connector for connecting the USB-serial data cable for programming and downloading data, and also for connecting a telemetry device such as an RF serial transmitter (not included). - 9 -...
- Page 10 STRONGLY recommend using an external power switch so you can turn off the Eggtimer while your model is undergoing the safety check by the RSO; in fact, most NAR and Tripoli sanctioned clubs require this. (The alternative is to have an external Reset switch/jumper;...
- Page 11 “safe” mode when multiple deployment systems are used; they cannot be triggered while the Eggtimer is reset. This can be used to put the Eggtimer in low power mode while it’s sitting on the pad for a long time, and can be released shortly before launch to help save battery life.
- Page 12 This is an extension of the on-board pizo buzzer. The on-board buzzer isn’t meant to be very loud, it’s designed to be used as an indicator when you’re right next to the Eggtimer to tell you that it’s ready, or to beep out the altitude after the flight. If you want to add a louder one, you can use these terminals.
- Page 13 Eggtimer web site (www.EggtimerRocketry.com) for details. Similarly you can also use the nice little sounders sold by Adept Rocketry, they make a very distinct sound that’s hard to miss even with other background noise present.
- Page 14 Because of the wide variety of rocket sizes and the different types of installations that are possible, the Eggtimer does not come with a battery. There are a wide variety of battery options available, which one you choose will depend on many factors: 1) The size of the rocket –...
- Page 15 LiPo batteries may show up to 4.2v when fully charged; that’s OK, the Eggtimer will be fine with it). If your battery reads under 2.8v, recharge it or dispose of it and use another battery. NEVER fly with a battery under 3.0v if you are using electronic deployment.
- Page 16 Programming Your Eggtimer Before you attempt to mount the Eggtimer in a rocket or fly it, you will need to know how the programming screens work. The Eggtimer can be programmed from just about any USB- compatible computer using the included USB-serial data cable.
- Page 17 Note that if you do not hit ANY keys or press the button down to select a pre-programmed flight profile, the Eggtimer assumes that you don’t have a PC connected and you are ready to start a flight. The beep-beep that tells you that you are in programming mode lasts for 30 seconds, then the Eggtimer begins the flight sequence.
- Page 18 A Launch Detect Altitude <50-500 by 50> Also called LDA, this sets the altitude Above Ground Level (AGL) that the Eggtimer uses to detect that a valid flight is in progress. It can be as low as 50’ or as high as 500’. It does several things: 1) Provides a start-of-flight reference point that other events are compared to.
- Page 19 This value is also used for the pre-launch sampling which occurs prior to Launch Detect, while the rocket is either sitting on the pad or is approaching LDA. Values are 4,5,10, 15, 20, 25, and 33 samples per second. Note that there is a finite amount of memory available for each flight, and using higher sample rates will consume more memory and may not necessarily produce a more “accurate”...
- Page 20 The Eggtimer will sample altitude at the descent sampling rate until either landing is detected, or it runs out of memory for that flight. Landing is detected when altitude readings of under 30 feet AGL are recorded for at least five seconds.
- Page 21 D Main Mode (0-Off, 1-Igniter, 2-Servo CCW, 3-Servo CW) E Main Altitude <100-2000 by 100, 0 @ Apogee> F Main On-Time <1-9, 0-Cont.> {only if Main Enable =1} F Servo PWM <0-9> {only if Main Enable = 2 or 3} This setting controls the Main (Channel A) deployment channel.
- Page 22 G CHB Mode (0-Off, 1-Igniter, 2-Servo CCW, 3-Servo CW, 4-Airstart, 5-Airstart w/o Breakwire,6-Delay) H CHB On-Time <1-9, 0-Cont.> {only if CHB Enable =1, 4, 5, or 6} H Servo PWM <0-9> {only if CHB Enable = 2 or 3} This setting controls the Channel B deployment channel. When set to “0”, the channel is turned off, so the other settings don’t matter.
- Page 23 I Burn Timer <100-20000 ms by 100> The Burn Timer is used to indicate to the Eggtimer what the burn time of your motor is. It is used to arm an airstart ignition on Channel B, and is also used to start Delay timer if CHB is in Delay mode.
- Page 24 In the case of the Eggtimer, the delay starts at the end of the Burn Timer, which starts from the last pre-LDA reading <= 5 ft rather than the actual ignition of the motor.
- Page 25 Data is streamed at 19,200 baud, 8 bits, one stop bit, no parity, no handshake, so you will need to make sure that your radio device is configured for that rate. The Eggtimer’s output signal is compatible with many common telemetry transponders such as the X-Bee and 3DR radios.
- Page 26 Note that if you abort a flight, for example you reset the processor after the Ready signal begins to sound, all of the settings including the Comments will be carried over to the next flight. If you want to change the Comments, you will need to go into the programming screen before the next flight.
- Page 27 As with any menu function, you will need to Reset the Eggtimer afterwards in order to begin a flight.
- Page 28 (assuming that you’re using switches for Power, Reset, and deployment battery power). Note: If you’re NOT using a Reset switch, the Eggtimer power should be the LAST thing you turn on… when you get the Ready chirp, you’re good to go.
- Page 29 The Eggtimer Flight Sequence At the Pad… As you know by now, when you first turn on the Eggtimer you get a long “I’m running” beep followed by 30 seconds of short beep-beeps to indicate that you’re in programming mode. When you’re at the pad and the programming beeps stop, that’s when the fun begins…...
- Page 30 LED outputs for this reason, so you can get a quick visual check of your deployment channels’ status. If for some reason you need to disconnect the deployment power, we STRONGLY recommend that you also Reset or power off the Eggtimer, so that you do not end up launching with the deployment power off.
- Page 31 To prevent this from happening, the Eggtimer uses a predictive mechanism to hold off deployments until it’s safely out of the mach “danger zone”. Real-time altitude readings are run through a filter, which “smoothes”...
- Page 32 If the rocket hasn’t gained any more altitude after one second then you must be starting on your way down, so the Eggtimer fires the drogue at that point, for a time determined by the CHB ON setting (or 3 seconds for a servo). Assuming that the mechanical portion of the drogue mechanism is working properly, your drogue chute will pop out and your rocket will start slowing down.
- Page 33 Once you’ve noted the maximum altitude so you can brag about it to your friends, you should turn off the Eggtimer as follows: Turn ON the Reset switch; this puts the Eggtimer in hold state Turn OFF the deployment batteries...
- Page 34 Downloading Flight Data The Eggtimer records your last 32 flights into its flight memory, reporting three types of data: Flight Settings – All of the settings on the Flight Settings menu (or the Presets, if you used one) Summary Data – Stuff like apogee, length of flight, maximum velocity, etc.
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Page 35: Table Of Contents
When you press the button to download the summary data, you will see something like this. Note that all times are in milliseconds, referenced from the t=0 sample (the last sample in pre-launch memory with an altitude <= 0). Flight Summary: Eggtimer Build_1.48b ...Comments:...flight 2013-04-28a F24 DD ...LDA <50-500 by 50>...100 ...Ascent Samp/sec: <4,5,8,10,15,20,25,33>...20... - Page 36 2.5 seconds would be 2500 milliseconds. The flight status is updated by the Eggtimer as the flight progresses, and saved into the flight memory. In the event that for some reason something goes wrong, you can use this value to help you figure it out.
- Page 37 To download the detail data, press the button again… you will see something like this. T,Alt,Veloc,KAlt,KVeloc,LDA,BurnT,LowV,Apogee,N-O,CHA,CHB 0,-10,-200.00,-0.48,-9.52,0,0,0,0,0,0,0 50,18,560.00,1.17,32.87,0,0,0,0,0,0,0 100,27,180.00,4.32,63.03,0,0,0,0,0,0,0 150,40,260.00,9.55,104.73,0,0,0,0,0,0,0 200,57,340.00,17.36,156.01,0,0,0,0,0,0,0 250,75,360.00,27.53,203.55,0,0,0,0,0,0,0 300,95,400.00,39.99,249.24,0,0,0,0,0,0,0 350,118,460.00,54.82,296.57,118,0,0,0,0,0,0 etc.. The first data field is the elapsed time in milliseconds, the second data field is the altitude in feet, and the third data field is the velocity in ft/sec.
- Page 38 You can clearly see that the rocket hits peak altitude at about 10 seconds, and maximum velocity at about 3 seconds. Note that the velocity graph is jaggedy compared to the altitude graph; this is due to the aforementioned issues with deriving velocity from barometric pressure. The important thing is that you can see clearly where the velocity peaks then drops sharply;...
- Page 39 Building Your Rocket to Use the Eggtimer Mounting In order to use your Eggtimer with a rocket, it will need to be properly mounted and secured. The Eggtimer is designed to be used with just about any rocket with a 1.35” dia. (BT-55) or larger payload bay, so any rocket that will take an egg will easily take the Eggtimer.
- Page 40 “drill out” to adjust), it might be a good idea to do this before you buy your motors, so you can purchase them with the correct delay time. Of course, if you’re using the Eggtimer for drogue deployment you don’t need to worry about this.
- Page 41 ON-Time to “continuous” (zero). That setting will keep it on until you reset the Eggtimer, or press the button at the end of the flight to beep out the maximum altitude. If you have a high-current load, like a solenoid, it WILL drain your deployment battery. Keep that in...
- Page 42 Note that most servos will run fine on a 3.7v Li-Po cell, a 3.6v NiMh pack, and any battery up to 6V. You can also use a small PX28 6v battery, the Eggtimer limits the travel time to 3 seconds, so it will probably last awhile. Nevertheless, like any deployment battery, you need to check it with a DVM before each flight.
- Page 43 For example, a small 5” payload bay 1.5” inches in diameter (inside of a BT-60 coupler…) 1) Length of Payload Bay in inches: 5 2) Diameter of body tube: 3) Square of #2 2.25 4) Multiply #1 and #3 11.25 5) Divide by 1500 .0075 6) Take the square root:...
- Page 44 Press BUTTON for 10 seconds to Reset To perform the reset, you need to hold the Button on the Eggtimer down for at least 10 seconds. When you do, you will hear a long confirmation tone, then you will see a progress screen as the memory pages are reset.
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Page 45: Memory Dump
Master Reset if you choose. To dump the memory, hold the Button down while the power is off or the Eggtimer is in reset mode, and continue to hold it down as you turn on the Eggtimer or release the reset. You will hear a long beep, acknowledging the Monitor mode, and you will see a “MON>”... - Page 46 To test the CHB “B” deployment channel, enter the monitor mode by holding the Button down while turning on the Eggtimer. You will hear a long beep, and you will see a MON> prompt on the terminal screen. Hit the “B” key, and you will hear a continuous warning beep. Press the...
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Page 47: Eggtimer Build_1.48B
Low-to-Medium Power Non-Deployment Example These settings will work fine for a small D-size rocket, or most E-G rockets. If the rocket is heavy, you might want to take the Ascent sample rate down a notch, to 5. Eggtimer Build_1.48b Flight Settings T:23.50 LDA <50-500 by 50>... -
Page 48: Interval(Ms)
High-Power Full Multiple Deployment Example This example is for a larger rocket using multiple deployment, with both channels of the Eggtimer being used to fire charges. Other than setting Channel B to fire at Nose-Over, it’s the same as the previous profile. - Page 49 Water rocketry is an art all to itself, if you haven’t looked at it lately do a little Google’ing… you’ll be amazed what they’re doing. The Eggtimer is the only flight computer that will modulate servos without any extra electronics. All you need is a 39 ohm ¼...
- Page 50 The Eggtimer requires three separate events, in order, for the igniter to be fired in Airstart mode: 1) The Breakwire must have been tripped, if this option was selected. This actually happens on the pad right after liftoff, but it doesn’t get checked until the Airstart Timer expires.
- Page 51 #3, and use a figure of about 60%-80% of that value. This will more or less ensure that the rocket isn’t going horizontal at burnout. Note that the Eggtimer has no way of knowing what direction your rocket is actually pointing, but this will at least ensure that the rocket hasn’t turned significantly horizontal before the second stage is ignited.
- Page 52 This example is for a rocket using Channel B in Airstart mode, with both channels of the Eggtimer being used to fire charges. In this case, the second stage motor’s built-in ejection charge will be used to fire the drogue, so you will need to model the flight carefully in order to select the correct delay.
- Page 53 Appendix E - Specifications Pressure Sensor: Type Bosch BMP-85/180, accuracy rated to approx. 9000 m (29,500 ft) Accuracy Approx 1m (3 ft) throughout rated pressure range Precision Approx ½ m (1.5 ft) throughout rated pressure range Processor Type Atmel ATMega328P Speed 16 MHz Memory...
- Page 54 Release the button, you will hear a long Beep, followed by a repeat of the Beep Code, then the Eggtimer halts. Perform a Reset or power it down and back up before flying.
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Page 55: Descent Samples/Sec <1,2,4,5,10
To enter Monitor Mode, connect the terminal cable, start your terminal program, and hold the Button down while powering on the Eggtimer. You will see a “MON>” prompt on your terminal screen. Hit the one-character monitor code to perform the function, some of them also require that you press the Button to start them;... - Page 56 • Press the Button to download the summary data in .TXT format • Close the capture buffer in your terminal program and save it to your computer as a .TXT file The Eggtimer is now ready to download the Flight Detail data… To download the Flight Detail data: •...