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• Hyper S3 Rocket - V3 Prototype conclusions

  stemforge.phil • 2 days ago • 0 comments

  The V3 Prototype is mostly successful with a few small changes taking place. 

  - The current sensing was not adequate. A redesign of the dual mosfet was needed, though this was a quick process.

  - Power Diodes were misaligned during manufacture. Consultation shows that I had created larger pads than required according to the datasheet, and this enabled the diodes to move and short. Simple change to diode footprint was needed.

  - Reverse polarity circuit was successful for the external Battery pin of the MODULE board, and I decided to incorporate this for the JST connector also to save the board (and battery) from wrong polarity. Even though the JST PH 2.0 connector is polarized, there is no standard. I have gone with the (Red on the Right) option, as looking at the connector. I'll put a small video on YouTube for those that need to adjust their LIPO battery pins.

  - With these few changes, the project is moving into pre-production status. The next board on order will have high quality ink, thicker internal copper and the changes mentioned. Also being tested is manufacturer's final board electrical testing, firmware flashing along with individual ESD packaging and package labelling. The next prototype is also going back to red and will have castellated pins for the four versions (LOGGER, DATA, CHARGE, MODULE).

  - Note, MODULE is the only version with the copper for batteries connected at the B+ pin. All other versions use the JST connector.

  - Did some flight testing yesterday (02-11-26) with the five boards made by JLCPCB. Fortunately I noticed three of the boards had misaligned sensors on the LOGGER. Sensors affected were the Magnetometer and the Barometric Pressure sensor. To move forward, I'm incorporating testing within the firmware for the LOGGER with the Flight Code so all sensors will be tested by the manufacturer before shipping to enhance the reliability. It's understandable with these tiny sensors, but not acceptable going ahead.
  

• PRECISE - Integrating the Truth - 10-DoF Sensor Fusion, No GPS Required

  stemforge.phil • 10/17/2026 at 03:45 • 0 comments

  Five Sensors, One Flight: Recreating a Water Rocket’s Path Without GPS (even when Hitting the 16 g Wall)

  Pump a soda bottle to 65 PSI, pull the pin, and the whole flight is over in seconds. No single sensor can tell you what happened in those seconds. The gyroscope drifts, the magnetometer is noisy, the accelerometer only knows “push,” and the barometer gets fooled by rushing air. But get them all talking to each other, and the HYPER S3 ROCKET can rebuild the entire flight in 3D, from pad to touchdown, without a single GPS fix.

  Five sensors, one truth: rebuilding the flight from the inside

  Here’s the part we’re most proud of. Every position in the 3D recreation (4:20) comes from the rocket’s own sensors working together. No GPS, no ground tracking, just correlated data and physics (5:16).

  Step 1: Find the horizon. Before you can say where a rocket went, you have to know which way is level. On its own, each sensor gets this wrong in its own way. The gyroscope reacts instantly to every twist and roll, but its small errors build up over time and the horizon slowly tilts away. The magnetometer gives an absolute reference to magnetic north that never drifts, but it’s too noisy to trust moment to moment. Fused together (5:33), each corrects the other. The gyro supplies the fast, smooth motion, and the magnetometer keeps pulling it back to a fixed heading. The result is a stable, level horizon reference that holds through stages of boost, coast and tumble.

  Step 2: Point the acceleration in the right direction. The accelerometer measures thrust along the rocket’s own body, and the rocket is pitching, rolling and weathercocking into the wind the whole time. Using the fused attitude from Step 1, every acceleration sample is rotated out of the rocket’s frame and into the oval’s frame: up, downrange and crosswind. Gravity is removed, and what’s left is the rocket’s true motion over the ground.

  Step 3: Integrate to velocity, then to displacement. Integrate that world-frame acceleration once and you get velocity. Integrate again and you get displacement, mapped onto real XY coordinates across the oval (5:24). This is dead reckoning, the same principle that guided aircraft and submarines long before satellites.

  Step 4: Cross-check against the barometer. Double integration is unforgiving, since any small error grows fast. So the vertical axis is checked against the barometric altimeter. Each sensor keeps the others honest: the barometer anchors height, and the inertial data exposes the altimeter’s pressure spikes at high speed (8:44).

  Gyro (fast) + Magnetometer (stable) ➔ Level horizon & attitude            ↓
  Accelerometer (body frame) ➔ rotated to oval frame ➔ minus gravity            ↓
  ∫ ➔ Velocity   ∫∫ ➔ Displacement (X, Y, Z)            ↓
  Barometer cross-check ➔ 3D flight path

  
  

  The payoff: a 3D flight recreation that follows the crosswind drift across the oval, with apogee within ±0.9 m and the landing point within ±4 m (9:49). That’s from a 4 gram board riding a fast soda bottle.

  For students, this is the magic moment. Calculus stops being abstract when the integral of your rocket’s acceleration draws your rocket’s path across the screen, then shows the stages one by one and even recreates the tumble to the ground. Want a softer landing? - sounds like a plan.
  

• PROTECT - The Battery in the Drawer is Everyone's Problem

  stemforge.phil • 10/10/2026 at 00:02 • 0 comments

  The Battery in the Drawer

  Battery safety is a habit, but some habits could be better
  Nothing dramatic happens to your pouch or 18650 lithium cell on the day it's ruined. There's no bang and no warning light. You put a gadget on a shelf or in a drawer with a little charge left, forget it for a few months, and when you come back the battery either won't charge, or charges and swells. That second outcome is the one worth worrying about. The damage was done weeks earlier, quietly, while everyone assumed the product was looking after itself.
  If you've built a battery-powered project, there's a good chance it's protected the way almost every tutorial and dev board shows: one device doing one job. That's a reasonable thing to do, but is it safe? This log is about why one device isn't enough, why that isn't anyone's fault, and what it takes to do better.
  Start with the safeguard most of us reach for first.

  
  Why deep sleep isn't off
  When the firmware sees a low voltage, say 3 V, it puts the microcontroller into its deepest sleep. It feels like switching the project off.
  But the power rail is still live, and a hidden quiescent floor keeps drawing life from the cell:

  • Linear regulators with permanently enabled paths. A common AMS1117 draws up to about 5 mA typical (check your part's datasheet).
  • A real-time clock, still ticking.
  • Fixed voltage dividers that act as a permanent leak to ground.

  Sleeping reduces the load. It doesn't disconnect it.
  The numbers are worth working out once. At 5 mA, a full 1000 mAh cell lasts about eight days. A nearly flat cell is a very different story: the stretch between "almost empty" and "damaged" holds only a small fraction of its capacity, and 5 mA can cover that quickly. And if the firmware hangs, nothing is watching at all.
  So software can't be the answer. Surely the hardware around it is.

  
  Why the charger doesn't help
  This is an easy mistake, and a very understandable one. A charging IC like the ubiquitous TP4054 sounds like battery protection for an 18650 or pouch, as it looks after the cell while charging. But it only manages charging. It isn't in the discharge path, so it never sees what the load does to the cell afterwards.
  Then there's the protection under the tape.

  
  Why the strip under the tape isn't the answer either
  Many pouch cells come wrapped in yellow Kapton tape, and under it there's often a small protection board (PCM). That's a good thing to have, and it's better than nothing. But from the outside you can't tell whether the tape hides a real protection IC, a dummy board or bare solder joints. And even a working one, like a standard DW01A setup, is a last-resort breaker designed to act at the cell's absolute limit. It was never meant to be a product's shutdown strategy.
  Each of these devices does its own job well. None of them was meant to be a lockout. Nobody has told us otherwise, because nearly every dev board and tutorial stops at one.
  And that leaves a flat battery. If only a flat battery were the worst of it.

  
  A dead cell isn't the worst outcome
  Cell datasheets set the discharge floor at about 2.5 V. Push a lithium cell well below that, toward 0 V, and leave it there for days, and its chemistry starts to change. Copper from inside the cell can dissolve into the electrolyte. Then someone does the natural thing and plugs it into a charger. During that recharge, the dissolved copper can plate back out as tiny metallic spikes that may grow through the separator and short the cell internally. In the worst case that means heat, gas and swelling, and sometimes fire.
  Most damaged cells never get that far. They just lose capacity and quietly become less trustworthy, which is the point: you can't see which cell is which. And many simple chargers don't check whether a cell has been pushed past the point of damage, since they were designed to charge cells, not to judge them.
  If you ever find a cell that's been left flat for a long time, or one that's started to swell, the safest advice is to retire it and...

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• Revisions for Latest Prototype and Rocket Launching tomorrow

  stemforge.phil • 10/09/2026 at 09:35 • 0 comments

  Prototype in manufacture includes a number of quality and functional revisions, including upgraded trace width to handle up to 3A in places where it's needed. Will be load testing and thermal testing this prototype within the next 2 weeks.

  The eFuse is a new addition as are a number of mosfets, the comparator and a supervisor chip.

  Reverse polarity even on the MODULE external B+ pin

  Got a new water rocket launcher yesterday and will get result up on youtube ASAP.

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