Launch Controller Design: Difference between revisions
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The purpose of a launch controller is to ignite a motor starter, and thus ignite a motor. There are several different kinds of starters, but they are fairly similar in electrical characteristics. When designing a launch controller, you will need to keep these in mind. | The purpose of a launch controller is to ignite a motor starter, and thus ignite a motor. There are several different kinds of starters, but they are fairly similar in electrical characteristics. When designing a launch controller, you will need to keep these in mind. | ||
'''Nominal resistance''' is just the resistance of the starter, including its leads. '''No-fire current''' is the ''maximum'' current that can be passed through the starter (to check continuity) when ignition is ''not'' intended. '''All-fire current''' is the ''minimum'' current that should be passed through the starter when ignition is intended. Therefore, the continuity circuit deliver less than the no-fire current to all starter types, and the ignition circuit must deliver more than the all-fire current to all starter types. | '''Nominal resistance''' is just the resistance of the starter, including its leads. '''No-fire current''' is the ''maximum'' current that can be passed through the starter (to check continuity) when ignition is ''not'' intended. '''All-fire current''' is the ''minimum'' current that should be passed through the starter when ignition is intended. Therefore, the continuity circuit must deliver less than the no-fire current to all starter types, and the ignition circuit must deliver more than the all-fire current to all starter types. | ||
There are still lots of blank cells in the table below - if you know where to find data on these, or would like to do some testing on your own and report your results, please contact [mailto:danno@danno.org Danno]. | There are still lots of blank cells in the table below - if you know where to find data on these, or would like to do some testing on your own and report your results, please contact [mailto:danno@danno.org Danno]. | ||
Revision as of 20:34, 18 January 2021
Motor starters (igniters)
The purpose of a launch controller is to ignite a motor starter, and thus ignite a motor. There are several different kinds of starters, but they are fairly similar in electrical characteristics. When designing a launch controller, you will need to keep these in mind.
Nominal resistance is just the resistance of the starter, including its leads. No-fire current is the maximum current that can be passed through the starter (to check continuity) when ignition is not intended. All-fire current is the minimum current that should be passed through the starter when ignition is intended. Therefore, the continuity circuit must deliver less than the no-fire current to all starter types, and the ignition circuit must deliver more than the all-fire current to all starter types.
There are still lots of blank cells in the table below - if you know where to find data on these, or would like to do some testing on your own and report your results, please contact Danno.
| Starter Type | Nominal resistance | No-fire current | All-fire current |
|---|---|---|---|
| AeroTech Copperhead | |||
| AeroTech First Fire | |||
| AeroTech First Fire Jr. | |||
| AeroTech First Fire Mini | |||
| Estes Model Rocket Starter | 0.5 - 2 ohms[1] | 1 amp[1] | |
| Estes Sonic | 1.6 ohms[2] | 1.25 amps[2] | 3.80 amps[2] |
| Firewire | 0.8 - 1.2 ohms[3] | 0.3 amps (less than 0.04 amps recommended)[3] | 0.6 amps (1 amp recommended)[3] |
| Firewire Mini | 0.8 - 1.2 ohms[4] | 0.3 amps (less than 0.04 amps recommended)[4] | 0.6 amps (1 amp recommended)[4] |
| MJG e-match (dip-your-own) | 0.8 - 1.3 ohms[5] | 0.3 amps[5] | 0.7 amps[5] |
| Quest First Fire Micro | |||
| Quickburst Twiggy | 1 - 2 ohms[6] | ||
| Quickburst Slim Gem | 1 - 2 ohms[7] | ||
| Quickburst Fat Boy | 1 - 2 ohms[8] | ||
| Quickburst Super Fat Boy | |||
| Wildman Big-Uns | |||
| Wildman Little-Uns | |||
| Wildman Tiny |
Note that proper continuity circuit design is much more critical from a safety standpoint; too little current from the ignition circuit just means the rocket doesn't launch, but too much current from the continuity circuit can cause unintended ignition! In general, test current should be the minimum required to activate whatever lamp or sound device you're using to signal continuity (for instance, this LED specifies 30 mA maximum, and this alarm element only requires 7 mA). You should really never be getting anywhere close to the no-fire limits listed above.
The maximum firing current you can deliver will probably have more to do with the characteristics of the battery being used than the design of the ignition circuit. (TODO: try to compile some data about different types of batteries.)
References
- ↑ a b https://www.apogeerockets.com/Rocket_Motors/Estes_Accessories/Estes_Starter_6pk (1/18/2021)
- ↑ a b c https://www.apogeerockets.com/Rocket_Motors/Igniters/Estes_Sonic_Starter (1/18/2021)
- ↑ a b c https://www.apogeerockets.com/Rocket-Motors/Motor-Starters/Firewire-Initiator-6-pk (1/18/2021)
- ↑ a b c https://www.apogeerockets.com/Rocket-Motors/Motor-Starters/Firewire-Mini-Initiator-6-pk (1/18/2021)
- ↑ a b c https://www.apogeerockets.com/Rocket-Motors/Motor-Starters/E-match-Starter-Kit (1/18/2021)
- ↑ https://www.apogeerockets.com/Rocket_Motors/Motor_Starters/Twiggy_Starter (1/18/2021)
- ↑ https://www.apogeerockets.com/Rocket_Motors/Motor_Starters/Slim_Gem_Starters (1/18/2021)
- ↑ https://www.apogeerockets.com/Rocket_Motors/Motor_Starters/Fat_Boy_Starters (1/18/2021)