Eggtimer Rocketry Eggtimer User Manual page 23

6
6
CHB Enable
2
3
The time and altitude of the CHB deployment are recorded in Flight Summary memory for later
downloading. Note that in the case of Airstarts at high speed, this data may not be accurate,
since aerodynamic effects may compromise the accuracy of the pressure-derived altitude
reading. Zeroes in these fields means that CHB didn't fire, either because it wasn't enabled or
because the conditions to fire CHB weren't met (i.e. Airstart Delay expired after Nose-Over).
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. The burn timer starts from the last pre-LDA sample <= 5 ft AGL and expires after
the selected time has elapsed from LDA. Technically, of course, the motor starts burning while
the rocket just leaving the pad, but for our purposes this is accurate enough since the time from
ignition to reaching 5 ft is typically a few hundred milliseconds or less.
In general, the Burn Timer value should be set to the rounded-down burn value of your motor.
For example, if your motor burns for 2.66 seconds, you should set the burn timer to 2600 ms (2.6
seconds). The Burn Timer is only used to trigger CHB in Airstart or Delay mode, so setting it
"incorrectly" will have minimal consequence on most flights; nonetheless, you should set it
correctly in order to get a better graph of your flight events.
Expiration of the Burn Timer and the altitude at the expiration of the Burn Timer are recorded in
the Flight Summary memory for downloading, and it is marked on the Flight Detail download.
J Airstart/Delay <0-9900 ms by 100> [CHB Mode = 4 or 5]
In CHB Airstart modes, the Airstart/Delay is used ensure that the second stage igniter doesn't
fire until the first stage motor has burned out. Used in conjunction with the Burn Timer, it
1-9 secs
0
Servo PWM
0-9
0-9
Deployment channel activated after expiration
of Burn Timer & Airstart/Delay for CHB-ON
seconds
Deployment channel activated after expiration
of Burn Timer & Airstart/Delay and held on
continuously until Reset
Deployment channel activated at Nose-Over
in servo mode, counter-clockwise, amount of
rotation controlled by Servo PWM setting
Deployment channel activated at Nose-Over
in servo mode, clockwise, amount of
rotation controlled by Servo PWM setting
- 23 -