Introduction Electronic devices to control certain events are called timers. These units allow a user to control events at a predetermined time setting. Rocketry devices incorporating timers are used to ignite upper stage motors in multi-stage rockets, ignite clusters of motors sequentially or for deployment of recovery devices. There are numerous units on the market, the ones listed below are a sampling of what is available.
Adept PST941 Timer
The PST941 Very High Current Staging/Deployment Timer from Adept is used to control staging in multi-stage rockets, airstarting motors or controling drogue and/or main chute deployment in high power rockets. The time is adjustable is 1/10 second increments up to a maximum of 25.5 seconds. There is a special PST941X model which allows one second timing intervals with a maximum of 255 seconds.
It has a piezo buzzer to indicate its operational status as well as igniter or deployment charge continuity.
Using a fully charged GE/Sanyo NiCad 9 volt battery, the timer can provide in excess of 12 amps of load current for a two second time period, which is sufficient to fire a cluster of most igniters or a large cluster of electric matches. Using a fresh alkaline battery, the timer will provide one amp of current for two seconds.
Dimensions are 2.25” wide by 1.25” thick by 2.5” high. Fits inside a 2.35” ID tube and weighs 2.5 ounces with battery installed.
Adept ASA3T Timer
The ASA3T Timer from Adept utlizes Adept’s first movement, liftoff detection mechanism together with adjustable components to form a timer. The liftoff detection mechanism is similar to an electronic mercury switch, detecting first movement in the rocket and passing that information on to the timing circuitry. If the unit does not detect acceleration for more than one half of a second, it will not begin the timing sequence, therefore it can not be accidentally armed. It can be set in 1/2 second increments from 1/2 second up to a maximum of 15 seconds.
It operates on external battery power at a voltage from 4.5 to 18 volts and can furnish greater than 10 amps, depending on the battery used. The unit features a power on LED indicator in addition to a continuity LED indicator. The blue rheostat on the right hand side is the timer setting adjustment and is adjusted with a small flat blade screwdriver.
Dimensions are 1.1” wide by .65” thick by 2.25” high. Fits inside a 1.11” ID tube and weighs .6 ounces.
The EZ Timer is a 2 channel programmable timer that can be used as a stand alone event sequencer or as a back-up to an altimeter. The desired time is easily set by using either the 4 buttons or a hand-held pendant. The programmed time is displayed in seconds for both channels on the 8 x 2 character, alpha-numeric LCD data screen.
The EZ-Timer includes local/remote power switch, local/remote launch detection, and screw terminals for flashbulb/igniter connections. If you specify at ordering, you can have special user defined on-screen text, such as “BOBS_ALT”or “If Found Call 555-1212” that is displayed during start-up.
Dimensions are 1.5” wide by 1.0” thick by 4.0” long. Fits inside a 1.52” ID tube and weighs 3.2 ounces with battery.