# I need a timer.

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#### n3tjm

##### Papa Elf
I am looking for a timer for a two stage rocket I mentioned in a different post. I need it to be affordable, able to fit in a 1" tube, and be in stock. I don't mind it being a kit. I prefer it being activated by break wire. Anyone have any suggestions?

Thanks

#### Voyager1

##### Well-Known Member
TRF Supporter
The three that come to mind are the Altus Metrum Easy Timer
the PerfectFlite MiniTimer 4
and the Missile Works PET2+
There are probably others.

#### James Duffy

##### Well-Known Member
+1 on the PerfectFlite miniTimer4. I've used it extensively and it has never failed me.

James

##### Well-Known Member
Without knowing what thread spawned this, I don't have the background for your requirements. That said, a breakwire is a pain to work with and prone to failure when compared to modern options. Accelerometer based trigger or integrated barometer based trigger, both with safety lockouts, can be had in the same footprint for somewhat similar costs so why not expand your options to include them?

#### n3tjm

##### Papa Elf
The thread that spawned this is Ed Millers Sonic Shock.

Reason why I like break wire is if the timer does not detect a launch for whatever reason, the second stage will never fire. The electronics will be in the booster. No electronics are going in the sustainer.

Break wire pretty much guarantees a launch detect. Its down side is you can have a premature second stage launch on the launch pad if the wire is broken prematurely. However, I think that is the lest hazardous risk since the rocket will still have stable flight and recovery. And the risk is minimal since the timer is the last thing that is armed and only once person has to be at the pad when that happens.

Easy Timer is to expensive for me.

I like the Pet2, a little on the pricy side but I'd consider it. (I used to have the first Pet timer and I loved it), looks like its OOP, and no one seems to have one in stock. The dual event capabilities would be a plus for my project too.

The miniTimer4 looks interesting.

Do you know if any of these timers can set off the igniters that come with Aerotech's 24mm loads?

#### cerving

TRF Supporter
The problem with breakwires as a staging timer trigger mechanism is that they are prone to accidental triggering. You need some kind of secondary safety, maybe a pullpin power switch, which would be the last thing that you would do before you leave the pad area. With an accelerometer and/or baro-altitude check, that can't happen. [Shameless plug: The Eggtimer Quantum will do the staging function, has breakwire verification and baro altitude and/or velocity qualifications, fits in a 24mm tube, and will light an Aerotech igniter (depending on your choice of battery). It can also be armed remotely via WiFi/browser from your phone, 100' away from your rocket. The kit is $40] #### n3tjm ##### Papa Elf Perhaps if you posted the .STL files, we could print and test it and get some feedback to you? The problem with breakwires as a staging timer trigger mechanism is that they are prone to accidental triggering. You need some kind of secondary safety, maybe a pullpin power switch, which would be the last thing that you would do before you leave the pad area. With an accelerometer and/or baro-altitude check, that can't happen. [Shameless plug: The Eggtimer Quantum will do the staging function, has breakwire verification and baro altitude and/or velocity qualifications, fits in a 24mm tube, and will light an Aerotech igniter (depending on your choice of battery). It can also be armed remotely via WiFi/browser from your phone, 100' away from your rocket. The kit is$40]
Wow. I didn't know the Eggtimer Quantum can do that. I just happen to have one. Looks like I am going have to get it out and play around with it. What is the Velocity qualification for starting the timer?

#### Charles_McG

##### Ciderwright
The altitude, vertical velocity (dAlt/dt), and breakwire qualifications are all checks that limit firing of the channel, not triggers that start the timer. The launch detect is an altitude threshold - configurable, but I don't recall the minimum. Once it crosses the LDA, the Quantum looks backwards in it's data to figure out when the flight actually started and uses that as the zero for the timing.

#### n3tjm

##### Papa Elf
Looking more into the Eggtimer Quantum, it looks like this might not be a good fit for this project.

#### bdureau

##### Well-Known Member
I have coded a timer that can be used with my AltiDuo board. Timer starts when the launch is detected using a barometer sensor. you can select different timing using some jumpers. If you need any more details send me a pm

#### cerving

##### Owner, Eggtimer Rocketry
TRF Supporter
The altitude, vertical velocity (dAlt/dt), and breakwire qualifications are all checks that limit firing of the channel, not triggers that start the timer. The launch detect is an altitude threshold - configurable, but I don't recall the minimum. Once it crosses the LDA, the Quantum looks backwards in it's data to figure out when the flight actually started and uses that as the zero for the timing.
The minimum LDA is 50', we generally recommend 100' or more. We put the 50' LDA in for someone who was using it in water rockets.

#### RocketTree

##### Well-Known Member
Bear altimeters has a timer for good value.

edit: just noticed this was already mentioned above!

#### n3tjm

##### Papa Elf
Problem is using a barometric sensor. It would be getting it's reading from the bottom of the rocket since the timer will be on the booster.

#### jderimig

If you are ok with breakwire, just use a cannon fuse that gets lit when the booster is lit. Very cheap and reliable. And much safer than a breakwire.

##### Well-Known Member
The Minitimer4 is accel based so that should give you better safety than breakwire and not need exposure to atmosphere.

I've used breakwire in the past and would roll my own with a accel or g-switch before going back to breakwire again.

#### n3tjm

##### Papa Elf
I've actually thought about doing just that. Similar to the old school staging back in the thermalite days. There are still obviously risks to doing that, which to me, are a lot more risky than break wire.

Probably should mention that this is a mid power rocket project. The rocket originally was built to fly on FSI 27mm Black Powder motors. Plan is to fly it on CTI 24mm F's