FAQ
TL;DR: DIY autonomous mower prototype runs 14 hours per dual-4S-10 Ah charge and covers ≈750 m²; "safety above all" [Elektroda, Marico, #20584525; Elektroda, Shadowix, #20254255].
Why it matters: Shows hobbyists can rival PLN 15 000 commercial robots for a fraction of the cost.
Quick Facts
• Cutting width: 36 cm [Elektroda, Marico, post #20584525]
• Runtime: 14 h on 2 × 4S 10 Ah Li-ion packs [Elektroda, Marico, post #20584525]
• Blade speed: 800–2 800 rpm; commercial Husqvarna spec 2 800 rpm [Elektroda, Marico, #20258661; Elektroda, kulfi27, #20260507]
• Drive system: scooter BLDC motors with Hall sensors + Chinese controllers [Elektroda, Marico, post #20253809]
• Boundary detection: Manchester-coded wire per US 8392044 patent [Elektroda, Marico, post #20253809]
How does the mower know when it crosses the boundary wire?
A PIC10F222 generator sends a 16-bit Manchester code through the loop. A coil on the mower compares received polarity; inversion shows it passed the wire, allowing ±5 cm precision regardless of soil moisture [Elektroda, Marico, post #20253809]
Why were BLDC motors with Hall sensors chosen over sensor-less types?
Hall feedback gives smooth low-speed starts, stable torque and silent commutation; sensor-less units stutter and knock at low revs [Elektroda, Marico, post #20253809] "Precise control in slow rpm ranges" was the deciding factor [Elektroda, Marico, post #20253809]
What navigation logic is currently implemented?
GPS first divides the lawn into two time-slots (≈600 m² and 150 m²). Inside each zone the mower drives in a pseudo-random ‘snake’ pattern, bouncing off wire and obstacles until the scheduled period ends [Elektroda, Marico, #20255079; #20584525].
How long does the battery last and how is it recharged?
Two parallel 4S 10 Ah packs power 14 hours of continuous mowing. The owner removes the mower nightly for bench charging via a CC/CV module monitored by ACS712 sensors; no dock is yet built [Elektroda, Marico, post #20584525]
Which material is used for the cutting disc, and why?
A CNC-cut polycarbonate disc enlarged to 20 cm radius holds three Landroid blades. Polycarbonate resists shattering from stones unlike acrylic, yet may be swapped later for a factory Worx disc [Elektroda, Marico, #20253809; #20254425].
What safety features are included?
The prototype already has an emergency mushroom, tilt sensor that halts the blade, and current-based stall detection. A planned guard will further shield fingers and improve mulching [Elektroda, Shadowix, #20254255; Elektroda, Marico, #20254319].
How fast should the blade spin for daily trimming?
Tests show acceptable cut quality below 1 000 rpm on light growth, while commercial Gardena/Husqvarna models target ~2 800 rpm for denser turf [Elektroda, Marico, #20258661; Elektroda, kulfi27, #20260507]. Adjust speed dynamically to save energy.
What type of charging contacts have proven durable outdoors?
Forum users suggest spring-loaded telescopic contacts from Fiat Seicento boot lights or Citroën Berlingo sliding doors; they self-clean and tolerate ≥5 A when paired with large docking plates [Elektroda, bobojad, post #20254025]
Which issues surfaced during field tests?
- Spinning blades occasionally mimic the 16-bit wire code, triggering false reversals (edge-case). 2. Front caster collects clippings and jams on wet ruts. 3. Ultrasonic HC-SR04 clones produced phantom echoes in open grass [Elektroda, Marico, post #20253809]
Can ultrasonic or IR sensors reliably spot small obstacles or animals?
Cheap HC-SR04 modules mis-trigger outdoors; narrow objects and cats often go unnoticed. Current monitoring on wheel motors now handles stalls more robustly [Elektroda, Marico, post #20253809]
How can I retrofit better front wheels for soft or wet ground?
Replace trolley casters with wide Landroid wheels set at a slight caster angle. This prevents sideways locking in ruts and reduces grass buildup [Elektroda, Marico, post #20584525]
Is building a DIY robot cheaper than buying?
For a complex plot a suitable commercial unit costs ≥PLN 15 000; the DIY solution reused scooter parts and cost "pennies" for motors and cells [Elektroda, Marico, #20255005; #20253809].
How to lay Manchester-coded boundary wire in three steps?
- Staple supply and return wires 5 mm apart along lawn edge; keep gaps ≥4 cm where you need detection.
- Form islands with omega loops; parallel legs cancel the field inside beds.
- Connect to 30 kHz Manchester transmitter and test polarity with the mower coil.
What firmware options exist for wheel control?
Open-source ‘bipropellant’ firmware runs on hoverboard driver boards, adding tilt sensing and button support for BLDC wheels [bipropellant GitHub, 2022; Elektroda, btsimonh, #20267092].
Could a solar panel extend runtime?
A small photovoltaic panel could trickle-charge while mowing, but at ≈10 W midday it adds only 70 Wh per day—just 5 % of a 4S-10 Ah pack [NREL, 2023]; still, it’s an “eco bonus” [Elektroda, szeryf3, post #20254917]
