So, what is this EasyTimer thingy?

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JimJarvis50

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I need to know a little more about the EasyTimer and there isn't much info on the AM website. I know it's a timer and can inhibit based on tilt. What I want to know is what other events or criteria can be used to inhibit. Specifically, Is it possible to inhibit based on an inertial velocity or altitude value?

Jim
 

mikec

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It doesn't have a barometric sensor so I'm guessing it's not able to do anything on altitude unless AltOS can use accel-based altitude. Documentation is up to the usual Altus Metrum standards :rolleyes:
 

JDcluster

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Yes, You can specify tilt angle to inhibit launch for staging. I have flown mine twice; once as an airstart cluster and second as a 2 stage with a Non-ignition second stage. There has been a firmware update and haven't flown it with the new firmware. On the cluster air-start flight; the ignition seems a bit later than usual.
 

ECayemberg

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Planning to trial for airstarts and staging in 2021. Curious as well...
 

Banzai88

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If you get one, make sure you update it to the latest firmware. The original release was sketchy in detecting launch.
 

JimJarvis50

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I realize that the device uses tilt to control inhibition. My questions is whether you can also use inertial velocity, or inertial altitude, or a flight event to inhibit in addition to tilt.

Jim
 

mikec

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Great questions, I think only AM knows. I would think that using inertial altitude would be a bad idea from a safety perspective, though, since it's mostly insensitive to tilt angle and so could be pretty nonsensical for a bad ascent. Unless there is more magic going on in the EasyTimer than I suspect.
 

UhClem

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While the firmware does compute a velocity and altitude, it is going to be of limited utility given the range limitations of the sensor.
 

JimJarvis50

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Great questions, I think only AM knows. I would think that using inertial altitude would be a bad idea from a safety perspective, though, since it's mostly insensitive to tilt angle and so could be pretty nonsensical for a bad ascent. Unless there is more magic going on in the EasyTimer than I suspect.
Yeah, I'm not a big fan of inertial altitude, but at least inertial velocity combined with time and tilt would capture most non-nominal flights situations. Since this device is programmed by computer, it would be great if someone could post the program screen.

Jim
 

JimJarvis50

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While the firmware does compute a velocity and altitude, it is going to be of limited utility given the range limitations of the sensor.
What do you mean by range limitation? Do you know if velocity and altitude can be used as inhibit criteria?

Jim
 

UhClem

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What do you mean by range limitation?
The sensor is a BMX160 with a best case range of +/-16G.

I would expect that running the GUI would answer any questions on inhibit criteria.
 

JimJarvis50

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The sensor is a BMX160 with a best case range of +/-16G.

I would expect that running the GUI would answer any questions on inhibit criteria.
Yeah, that sensor range could be an issue for some flights. I don't have an EasyTimer myself or I would run the interface (I'm evaluating other projects). As per above, it would be great if someone could post a screenshot.

Jim
 

mikec

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Everything listed is a configurable option.
Interesting. I'd love more details from AM about how these are implemented and how they were validated. For example, is the height above pad corrected for the tilt angle?
 

Cameron Anderson

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Just remember to check the AM definitions of flight states when you set the timer. And dont use your "ascent" setting for your "acceleration" setting.
I like the EasyTimer but the system is not as intuitive as the instructions make it seem.
 

JimJarvis50

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Any thoughts on what settings you would use for staging?
Well, now that I know how closely it resembles the EasyMega, it's pretty easy for me to define the settings. I have a few preferences on staging strategy. One preference is to use time from launch as the actual trigger, as opposed to burnout plus a delay or some other trigger. I think that gives better control over the timing of the flight. It is also my preference to use an altitude check if possible, although I am willing to relax the altitude criteria if tilt is also a criteria. Assuming that the height calculations is as it appears (an inertial calculation of altitude), then I would do my flight simulation and determine the time where I wanted the sustainer igniter to fire. Let's say as an example that I want to light the sustainer igniter at 15 seconds and I predict the altitude to be 10,000 feet at that point, then I would set:

- Time from launch > 15 seconds
- Time from launch < 16 seconds (to close the firing window - very important)
- Height > 7,000 feet
- Angle < some value between 8 ad 20 degrees, depending on altitude and location
- 1 burnout (I flip/flop on this one)
- No delay after last condition
- No "states" used
- Shortest or nearly shortest pyro firing time

If I was using the B channel for the separation charge, I would just use 1 burnout + 2 second delay and maybe time from launch < something.

Jim
 

OverTheTop

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One way I used a TeleMega for sustainer ignition was to parallel the two deployment channels. One was set on a timer but with a lockout at 20deg, the other was set to trigger after a time and if the sustainer got to 15deg, and was also inhibited if greater than 20deg. That way if the flight was straight the timer ignited at the designed time, but if the flight started to tilt it would ignite earlier but before it got to the 20deg lockout.
 

JDcluster

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This timer doesn't have a Baro unit on it. You can not use altitude parameters.

Well, now that I know how closely it resembles the EasyMega, it's pretty easy for me to define the settings. I have a few preferences on staging strategy. One preference is to use time from launch as the actual trigger, as opposed to burnout plus a delay or some other trigger. I think that gives better control over the timing of the flight. It is also my preference to use an altitude check if possible, although I am willing to relax the altitude criteria if tilt is also a criteria. Assuming that the height calculations is as it appears (an inertial calculation of altitude), then I would do my flight simulation and determine the time where I wanted the sustainer igniter to fire. Let's say as an example that I want to light the sustainer igniter at 15 seconds and I predict the altitude to be 10,000 feet at that point, then I would set:

- Time from launch > 15 seconds
- Time from launch < 16 seconds (to close the firing window - very important)
- Height > 7,000 feet
- Angle < some value between 8 ad 20 degrees, depending on altitude and location
- 1 burnout (I flip/flop on this one)
- No delay after last condition
- No "states" used
- Shortest or nearly shortest pyro firing time

If I was using the B channel for the separation charge, I would just use 1 burnout + 2 second delay and maybe time from launch < something.

Jim
 

Crumb fire

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This timer doesn't have a Baro unit on it. You can not use altitude parameters.
Right, but why is there a ''height above pad'' treshold ? maybe it calculate altitude by acceleration?

Steeve
 

mikec

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FWIW, I dug into the AltOS source code and the Kalman filter does appear to estimate height on a product like the Easytimer with only an accelerometer. See altos-1.9.6/src/kernel/ao_kalman.c

I didn't spend enough time looking to tell if this estimate was being corrected for attitude on units that have gyros.
 

JimJarvis50

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This timer doesn't have a Baro unit on it. You can not use altitude parameters.
Inertial velocity and altitude are easily calculated from acceleration data. The values may not be very accurate if the accelometer itself is in error (as was the case for many of the Ravens a few years ago) or if the flight is not vertical. However, if the tilt isn't that much (<20%), there isn't that much error in the values and certainly not enough error to prevent an effective "altitude check". All of this assumes that the "height" criteria is indeed accelerometer-based altitude and that the range of the accelerometers is not limited as was mentioned previously. I don't know the answers to those questions, but at face value, it looks to me like altitude could be used. Keith says that he will try an update the description, but he doesn't know when.

Jim
 

n27sb

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Does anyone have any recent experience with the Easy timer and any recommendation on airstart cluster settings
?
 

Not Quite Nominal

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One way I used a TeleMega for sustainer ignition was to parallel the two deployment channels. One was set on a timer but with a lockout at 20deg, the other was set to trigger after a time and if the sustainer got to 15deg, and was also inhibited if greater than 20deg. That way if the flight was straight the timer ignited at the designed time, but if the flight started to tilt it would ignite earlier but before it got to the 20deg lockout.
How did you parallel the two channels? Simply wire one ematch up to both channels?
I am thinking of dipping two ematches (slightly staggered) into one head of pyrogen, and having one ematch on each channel.
The goal here is to have something similar to Marsa's "try" functionality, with two firing conditions:
  1. Starting to tilt, but still safe
    1. Above minimum ignition altitude
    2. Tilt greater than optimal (> 10 degrees)
    3. Tilt less than the unsafe condition (< 20 degrees)
  2. Optimal ignition
    1. At optimal ignition altitude
    2. Tilt less than the unsafe condition (<20 degrees)
 

OverTheTop

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How did you parallel the two channels? Simply wire one ematch up to both channels?
Both channels were paralleled at the TeleMega. The igniter in the motor was one standard igniter for the M motor, in parallel with an eMatch as backup. The igniters were also augmented with most of an E28 Blue Thunder grain.
 

H_Rocket

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I have two of the easy timers and can't get them to work. If anybody has and is willing to share any tricks, I'd be grateful.
 

n27sb

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I have two of the easy timers and can't get them to work. If anybody has and is willing to share any tricks, I'd be grateful.
I should have mine in a few days, I'll let you know what I learn
 

H_Rocket

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I should have mine in a few days, I'll let you know what I learn
Thanks Steve, I've tried contacting Altus Metrum and posted to their Facebook page. I can power it up, get some beeps, but I can't get it to appear in the AltOS application for programming.

You can PM me if you like.
 

n27sb

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I am assuming that it is similar to the EasyMini that I use. Sometimes it is a little fussy about the computer seeing it.Try plugging in the USB and then powering the Timer. Then select configure. That should do it.
If not, try a different USB cable.
 
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