h2guard

item,qty,spec,supplier,unit_cost_usd,make_buy,notes
1 Detector head enclosure,1,"ABS or polycarbonate box 110 x 80 x 90 mm, two 26 mm sensor ports in the floor, cable gland, wall plate; see HGD-DWG-001",Electronics distributor,8.00,buy,Indicative price; sensor ports 175 mm below the ceiling directly above the likely leak source
2 Catalytic hydrogen sensor,1,"Catalytic (pellistor) combustible gas sensor with hydrogen response, 0 to 100 % LFL, for example Figaro TGS6812-D00, on a small carrier board with bridge supply",Electronics distributor (Figaro),35.00,buy,Indicative price; primary trip sensor; t90 and power still to be confirmed from the datasheet (HGD-CAL-001)
3 MOS hydrogen sensor,1,"Metal oxide hydrogen sensor, about 30 to 3000 ppm, for example Figaro TGS2616-C00, 5 V heater about 280 mW",Electronics distributor (Figaro),15.00,buy,Indicative price; early warning and trend only; never used alone to trip
4 Flame arrestor discs and bump test cup,1,"Two sintered stainless steel discs 25 mm diameter x 2 mm, pore size 50 um or less, sensor can within about 2 mm behind each disc; drip skirt 96 x 66 x 22 mm molded as the bump test cup with a 6 mm gas nozzle",Industrial filter supplier; 3D print for the cup,7.00,buy,Indicative price; disc thinned from 5 mm to 2 mm (HGD-CAL-001 F1 and F2); not a certified flameproof assembly
5 Controller enclosure,1,"IP65 polycarbonate wall box 200 x 250 x 90 mm with cable glands, top at least 1 m below the ceiling",Electronics distributor,15.00,buy,Indicative price
6 Controller board,1,"RP2040-class microcontroller with 4 MB flash or more; sensor bridge and heater drivers; hardware window comparator with a hardware latch driving a relay in series with the microcontroller's valve MOSFET; fan PWM and tachometer; alarm outputs; 1 s watchdog",Electronics distributor; prototype board,25.00,make,Indicative parts price; circuit is a block diagram at TRL 3; firmware limited to a labeled sketch
7 Front panel,1,"Small OLED display, key-switch reset, test button, three status LEDs",Electronics distributor,12.00,buy,Indicative price
8 24 V DC power supply,1,"Certified plug-in or desktop supply, 24 V, 2.5 A (60 W), with DC plug",Electronics distributor,15.00,buy,Indicative price; keeps mains out of the self-built parts; peak load about 48 W (HGD-CAL-001 H2)
9 Exhaust fan,1,"150 mm mixed-flow EC duct fan, 24 V, about 450 m3/h free air and 200 Pa shut-off, PWM speed input and tachometer output; inside grille, wall sleeve, backdraft shutter and weather hood",HVAC supplier,50.00,buy,Indicative price; re-specified from a 300 m3/h axial fan that cannot reach the 300 m3/h boost against the duct losses (HGD-CAL-001 G3); not rated for hazardous areas
10 Make-up air grille,1,"Low-level wall grille 300 x 160 mm with insect mesh, about 50 % free area",Hardware store,8.00,buy,Indicative price; on the far side of the room from the fan
11 Normally closed solenoid valve,1,"2/2-way, normally closed, direct acting, 1/4 in, brass body with FKM seals, 24 V DC coil about 8 W, 0 to 10 bar, Zener clamp for fast closing",Pneumatic or valve supplier,30.00,buy,Indicative price; hydrogen compatibility and seat leak rating to be confirmed; certified gas valves cost several times more
12 Sounder and beacon,1,"24 V DC combined sounder (about 90 dB at 1 m) and red flashing beacon",Electronics distributor,12.00,buy,Indicative price; top 450 mm below the ceiling by the door
13 Cable and conduit,1,"Four-core and two-core cable, about 15 m total, cable glands, surface conduit",Electronics distributor,15.00,buy,Indicative price; no exploded-view callout
14 Hardware and consumables,1,"Screws, wall plugs, ferrules, heat-shrink, labels",Hardware store,8.00,buy,Indicative price; no exploded-view callout
15 Bump test port and tube,1,"Bulkhead push-fit test port with dust cap beside the controller, about 3 m of 4 mm OD x 2.5 mm bore PTFE or PA tube to the cup nozzle, clips",Pneumatic fittings supplier,9.00,buy,Indicative price; new at TRL 3 to meet R12; span gas and its regulator are not included