Launch Controller Design
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, so in designing a launch controller, it is important to know which types it will and will not accommodate.
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. 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).
| Starter Type | Nominal resistance | No-fire current | All-fire current |
|---|---|---|---|
| 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 Initiator | 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 Initiator | 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 | |||
| Wildman Big-Uns motor lighter | |||
| Wildman Little-Uns motor lighter | |||
| Wildman Tiny motor lighter | |||
| Wildman ejection lighter |
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)