Units Affected: All RocKontrollerTM 1
Date Issued: 08-10-12
Date Updated: 01-01-13
Issue: Live output at startup (see update below)
It has been observed by one user that the ignition output from their PAD unit was live, i.e., supplying ignition power at the ignition cable connector whenever the unit was turned on. This was independent of the state of the LCO unit which was turned off during the users’ observation. The condition occurred shortly after the users’ successfully performed some initial testing of a new system.
Once the problem showed up, it continued to malfunction for several more tests. The unit was returned to Rocket Electronics (RE) for trouble-shooting/repair. The most likely problems being either a shorted ignition output FET or, a false trigger condition on the gate of the FET (the circuit that causes the FET to activate) due to a defective board or microcontroller unit (MCU).
The unit was tested upon return to RE and initially found to be working correctly.
The unit was then placed in a very warm environment and the malfunction was observed twice during a series of more than 100 trials/tests of cycling the unit ON, then OFF.
When the second instance occurred, the unit was left running and it was determined that the port on the MCU that activates the FET gate was ON, that is, the output FET was not malfunctioning or shorted, but rather it was responding to a trigger signal from the MCU.
The likelihood of your unit experiencing this condition is extremely remote, but possible.
Further review and testing indicates the problem is an issue with timing/sequence issues and certain runs of the MCU hardware used in production of the RocKontroller 1.
A software/firmware modification of the code that assigns parameters to the affected MCU port was made that will preclude this possibility. Exhaustive testing was performed to assure that the condition is resolved.
Effect on Usability:
Recommend having PAD unit firmware updated.
PAD units should be returned to Rocket Electronics for a firmware update.
No return authorization is required to fix this problem for an existing Rocket Electronics customer. Simply return the PAD unit only, along with the following information:
Return Address ______________________________________
PAD Serial Number ______________________________________
Rocket Electronics LLC
8400 N. Magnolia Ave., Suite J
Santee, CA 92071
We will ship your unit to you by the week of August 27, 2012 or within 2 days of receipt, whichever occurs later. You will be compensated for the shipping charge you incurred and the return shipping will be prepaid. While back at Rocket Electronics, your unit will also be upgraded with the enhancement described below.
The likelihood of a defective, shorted ignition output FET switch is remote. This could occur due to an extraordinary current draw through the switch, or the FET switch could simply fail.
In the design of the RocKontroller 1, if the FET is subjected to such a condition, e.g., due to a shorted ignition cable either during testing or flight activity, the internal fuse will blow.
The chance of the FET itself just spontaneously failing is extremely unlikely, but possible.
During the course of resolving this issue, we discussed a possible enhancement to the RocKontroller 1 that would allow us to provide a pre-flight test to detect and report a shorted output FET switch. With the addition of a couple components and a firmware modification, we can provide such a test, one similar to the pre-flight test performed by the RockeTiltometer 2 to detect a shorted/live output at startup:
With the igniter cable NOT connected to the RocKontroller 1, turning on the PAD unit will immediately test for a shorted ignition FET switch. If the output FET is on/shorted, the unit will sound repeated beeps and flash the READY LED. This will continue until the unit is turned off. In this case the unit should be returned for repair.
Additionally, a test will be performed that tests for a premature connection of the igniter cable that is either shorted or connected to an igniter. If such a condition is detected, the beeper will pulse and the CONTINUITY LED will flash repeatedly until the unit is turned off. In this case, remove the igniter cable and restart the unit.
UPDATE - 01-01-2013: It has been reported by a user that on at least one occasion, it is still possible for a small current, but sufficient to fire an ematch, to exist on the output prior to the continuity check being performed when the PAD unit is turned on. So, if a user ignores proper procedure and connects the igniter to the PAD unit prior to turning the PAD unit on, it is possible to fire a low-current device such as an ematch by turning the PAD unit on. The chance of this occurring is very small, but possible, even with the above modifications in place. If your device displays such behavior, contact RockeTiltometer.com and arrange for an RA to return the system for a refund.
Though we cannot control someone not properly testing for a live output prior to connection of an igniter to any launch controller, these enhancements to the RocKontroller1 will provide an extra measure of safety for the prudent rocketeer not available elsewhere in the hobby.