Custom ESC for Powered Glider
Budget: $250 – $750 USD
ESC Target Specification (F5J / 50A Class)
0) Summary
Goal: Lightweight, reliable 50A brushless ESC for F5J gliders, similar class to “Francy 50” with features I use on Castle 50 Light.
Priorities: (1) Reliability & clean BEC power, (2) Low weight, (3) Strong brake for fast prop fold, (4) Smooth startup, (5) Clear programmability.
1) Electrical Ratings (Must-Have)
Battery: 2–6S LiPo / Li-ion (protected against reverse polarity).
Current: 50A continuous (at 25 °C ambient, adequate airflow)
65–80A burst for ≥10 s, specify exact profile and test conditions.
ESC Efficiency: ≥98% at 20–30A, ≥96% at 50A (measure + report).
Switching Frequency: 16–32 kHz (engineer to specify; justify choice for outrunner efficiency & acoustic profile).
BEC (internal, switching):
Output: Selectable 5.5 V / 7.4 V / 8.4 V
Continuous: 5 A (min), Peak: 10 A (≥1 s)
Ripple: <50 mVpp @ 2 A load (report with scope shot).
Brown-out immunity: hold-up during throttle punches @ low pack voltage.
If BEC is not feasible at the weight target, offer No-BEC “Opto” variant as Option B.
Input Capacitance: Low-ESR electrolytic/polymer bank sized for 50A with 20 cm leads; specify total µF and ESR. Mount for serviceability.
2) Mechanical & Weight (Must-Have)
Target Weight: ≤ 25 g including BEC and heatshrink (no connectors).
(If >25 g, provide best achievable weight and tradeoff notes.)
Size Envelope: Max 55 × 22 × 10 mm (L×W×H) preferred; provide drawing.
Leads:
Battery & Motor: High-strand silicone 14 AWG (200 °C) preferred; if proposing 16 AWG, show temperature rise at 50A continuous.
BEC/Signal: 22–26 AWG silicone.
Cooling: Heat spreader or copper pour to keep MOSFET case <85 °C at 50A in 2 m/s airflow. Provide thermal test.
3) Control & Flight Features (Must-Have)
Brake: Strong “prop-fold” brake with immediate ramp, user levels (incl. 80–100%).
Startup: Smooth soft-start; no cogging with large F5J props.
Timing: Auto timing + fixed options (5°, 10°, 15°).
Cutoffs:
Voltage cutoff: hard motor stop at user-set threshold (per-cell detection).
Current limit: soft-rolloff (“third-stage cutoff”), no hard cut mid-climb.
Thermal: adaptive derate; user option to disable.
Rotation: CW/CCW selectable.
Throttle Calibration: Auto + manual.
Data/Programming: Programming card or USB/UART app; settings stored in NVM.
4) Protections & Robustness (Must-Have)
Desync protection, stalled-rotor handling (no MOSFET death).
Over-voltage, under-voltage, over-current, over-temp.
Gate driver Miller clamp or equivalent to prevent shoot-through.
Input reverse polarity protection (diode-less preferred to avoid loss; propose solution).
Brown-out safe reboot (motor stays off on reset).
5) Firmware & Telemetry (Nice-to-Have)
Telemetry (voltage, current, ESC temp, RPM) over standard protocol (e.g., FrSky S.Port / SRXL2 / UART—state what’s feasible).
Field updatable firmware (DFU/bootloader).
Governor mode not required for F5J, but OK if it comes “for free.”
6) Components (Engineer to Propose + Justify)
MOSFETs: Part numbers, Rds(on) @ gate drive, package, thermal rating.
Gate Driver: Part number, dv/dt immunity.
MCU: Part number, PWM resolution, timers.
Input Caps: Type, total µF, ESR @ 100 kHz.
BEC: Controller IC, inductor specs, ripple data.
7) Deliverables & Milestones
M1 – Design Pack (paid milestone):
Block diagram, schematic, BOM with part numbers & ratings, mechanical drawing.
Written explanation (plain English) of key design choices (MOSFETs, switching freq, BEC topology, input caps).
Test plan (see below).
(Payment on acceptance of M1.)
M2 – Prototype (paid milestone):
2–3 working samples + programming method.
Test report with scope captures: input ripple @ 30A & 50A, BEC ripple @ 2A & 5A, thermal graph at 50A, current limit behavior, brake performance.
Firmware/settings sheet.
(Payment on delivery + tests meeting spec.)
M3 – Rev-B (optional):
Weight/thermal/firmware refinements based on flight feedback.
8) Acceptance Tests (Bench + Flight)
Voltage cutoff accuracy: per-cell detection within ±0.05 V.
Current limit profile: soft-rolloff; no hard cut until user-set threshold exceeded by >20% for >1 s.
BEC stability: <50 mVpp ripple at 2 A; holds 5 A continuous @ 6S input without thermal shutdown.
Thermals: At 50A/6S, FET case <85 °C with 2 m/s airflow for 60 s climb.
Brake: From 50% throttle to stop: time-to-fold measurement with 13–14″ folding prop.
Noise/EMI: No receiver brownouts; document wiring and caps used.
9) Manufacturing & Quality
Assembly: Lead-free, reflow + AOI.
Conformal Coat: Optional; provide variant.
Serial/Batch Tracking: Yes.
Documentation: PDF user manual + settings table.
10) What to Include in Your Quote
Confirm what you meet vs propose to change.
Exact weight and dimensions you can achieve.
Part list (key components) and availability risk.
Timeline for M1/M2.
Warranty on prototypes and production.
0) Summary
Goal: Lightweight, reliable 50A brushless ESC for F5J gliders, similar class to “Francy 50” with features I use on Castle 50 Light.
Priorities: (1) Reliability & clean BEC power, (2) Low weight, (3) Strong brake for fast prop fold, (4) Smooth startup, (5) Clear programmability.
1) Electrical Ratings (Must-Have)
Battery: 2–6S LiPo / Li-ion (protected against reverse polarity).
Current: 50A continuous (at 25 °C ambient, adequate airflow)
65–80A burst for ≥10 s, specify exact profile and test conditions.
ESC Efficiency: ≥98% at 20–30A, ≥96% at 50A (measure + report).
Switching Frequency: 16–32 kHz (engineer to specify; justify choice for outrunner efficiency & acoustic profile).
BEC (internal, switching):
Output: Selectable 5.5 V / 7.4 V / 8.4 V
Continuous: 5 A (min), Peak: 10 A (≥1 s)
Ripple: <50 mVpp @ 2 A load (report with scope shot).
Brown-out immunity: hold-up during throttle punches @ low pack voltage.
If BEC is not feasible at the weight target, offer No-BEC “Opto” variant as Option B.
Input Capacitance: Low-ESR electrolytic/polymer bank sized for 50A with 20 cm leads; specify total µF and ESR. Mount for serviceability.
2) Mechanical & Weight (Must-Have)
Target Weight: ≤ 25 g including BEC and heatshrink (no connectors).
(If >25 g, provide best achievable weight and tradeoff notes.)
Size Envelope: Max 55 × 22 × 10 mm (L×W×H) preferred; provide drawing.
Leads:
Battery & Motor: High-strand silicone 14 AWG (200 °C) preferred; if proposing 16 AWG, show temperature rise at 50A continuous.
BEC/Signal: 22–26 AWG silicone.
Cooling: Heat spreader or copper pour to keep MOSFET case <85 °C at 50A in 2 m/s airflow. Provide thermal test.
3) Control & Flight Features (Must-Have)
Brake: Strong “prop-fold” brake with immediate ramp, user levels (incl. 80–100%).
Startup: Smooth soft-start; no cogging with large F5J props.
Timing: Auto timing + fixed options (5°, 10°, 15°).
Cutoffs:
Voltage cutoff: hard motor stop at user-set threshold (per-cell detection).
Current limit: soft-rolloff (“third-stage cutoff”), no hard cut mid-climb.
Thermal: adaptive derate; user option to disable.
Rotation: CW/CCW selectable.
Throttle Calibration: Auto + manual.
Data/Programming: Programming card or USB/UART app; settings stored in NVM.
4) Protections & Robustness (Must-Have)
Desync protection, stalled-rotor handling (no MOSFET death).
Over-voltage, under-voltage, over-current, over-temp.
Gate driver Miller clamp or equivalent to prevent shoot-through.
Input reverse polarity protection (diode-less preferred to avoid loss; propose solution).
Brown-out safe reboot (motor stays off on reset).
5) Firmware & Telemetry (Nice-to-Have)
Telemetry (voltage, current, ESC temp, RPM) over standard protocol (e.g., FrSky S.Port / SRXL2 / UART—state what’s feasible).
Field updatable firmware (DFU/bootloader).
Governor mode not required for F5J, but OK if it comes “for free.”
6) Components (Engineer to Propose + Justify)
MOSFETs: Part numbers, Rds(on) @ gate drive, package, thermal rating.
Gate Driver: Part number, dv/dt immunity.
MCU: Part number, PWM resolution, timers.
Input Caps: Type, total µF, ESR @ 100 kHz.
BEC: Controller IC, inductor specs, ripple data.
7) Deliverables & Milestones
M1 – Design Pack (paid milestone):
Block diagram, schematic, BOM with part numbers & ratings, mechanical drawing.
Written explanation (plain English) of key design choices (MOSFETs, switching freq, BEC topology, input caps).
Test plan (see below).
(Payment on acceptance of M1.)
M2 – Prototype (paid milestone):
2–3 working samples + programming method.
Test report with scope captures: input ripple @ 30A & 50A, BEC ripple @ 2A & 5A, thermal graph at 50A, current limit behavior, brake performance.
Firmware/settings sheet.
(Payment on delivery + tests meeting spec.)
M3 – Rev-B (optional):
Weight/thermal/firmware refinements based on flight feedback.
8) Acceptance Tests (Bench + Flight)
Voltage cutoff accuracy: per-cell detection within ±0.05 V.
Current limit profile: soft-rolloff; no hard cut until user-set threshold exceeded by >20% for >1 s.
BEC stability: <50 mVpp ripple at 2 A; holds 5 A continuous @ 6S input without thermal shutdown.
Thermals: At 50A/6S, FET case <85 °C with 2 m/s airflow for 60 s climb.
Brake: From 50% throttle to stop: time-to-fold measurement with 13–14″ folding prop.
Noise/EMI: No receiver brownouts; document wiring and caps used.
9) Manufacturing & Quality
Assembly: Lead-free, reflow + AOI.
Conformal Coat: Optional; provide variant.
Serial/Batch Tracking: Yes.
Documentation: PDF user manual + settings table.
10) What to Include in Your Quote
Confirm what you meet vs propose to change.
Exact weight and dimensions you can achieve.
Part list (key components) and availability risk.
Timeline for M1/M2.
Warranty on prototypes and production.