IoT Fire Alarm Device Design
Thought for 8 sec
You should ask Quectel / supplier for the EC25MXGA hardware design package, not just the marketing datasheet.
Ask for:
-
EC25MXGA Hardware Design Guide
- Full pin descriptions
- Power supply requirements
- PWRKEY / RESET timing
- UART / USB / SIM / RF reference circuits
- VDD_SDIO usage guidance
-
Recommended PCB land pattern / footprint
- Pad dimensions
- Pad numbering
- Paste mask / solder mask recommendations
- Keepout zones under/around the module
- Assembly notes
-
Reference schematic
- VBAT_RF / VBAT_BB decoupling
- SIM socket wiring
- Antenna matching / ESD
- Status pins
- Power-on/off sequence
-
RF layout guidelines
- 50 Ω antenna routing
- Ground stitching via recommendations
- Antenna connector/matching network placement
- Diversity/GNSS pins if used or unused
-
Certification documents
- RCM / ACMA / AS/CA S042 relevance
- Carrier approval info for Australia
- LTE band support for AU carriers
- Test reports if available
-
Lifecycle / supply confirmation
- Active production status
- Recommended replacement if EC25MXGA is not preferred
- Minimum order / lead time
Short message you can send:
We are designing a dual-modem Australian fire alarm signalling device using 2 × EC25MXGA. Please provide the EC25MXGA hardware design guide, recommended PCB land pattern/footprint, reference schematic, RF layout guide, SIM interface recommendations, VDD_SDIO connection guidance, Australian carrier/certification documentation, and lifecycle/supply status.
Ok I’ll contact them
Thought for 14 sec
Good plan. Ask them specifically for the hardware design guide + recommended PCB land pattern for EC25MXGA-128-SNNS.
Until we get that, the safest path is:
- Keep EC25MXGA in the design.
- Do not send the PCB to manufacture yet.
- Continue with placement/routing cleanup only as a draft.
- Finalize modem footprint, SIM wiring, RF layout, and
VDD_SDIOtreatment once Quectel confirms the official guidance.
Clean draft layout
Review EC25 wiring
Check power budget
Update factory checklist
Run current checks
Refine this doc
Ask about this doc
Centaur-Style 8 Input Supervision Notes
Source
- User-uploaded
Installation_Guide_2_7_Melb.pdf, OCR-extracted. Critical wiring values must be checked against the original diagrams/images before final schematic capture.
User direction
The 8 inputs in this design should work like the Centaur/installation guide inputs, including the different wiring colours and resistor/supervision behavior.
Extracted input architecture
The guide describes Alarm System Inputs using a two-wire ASE input pair connected to an End-of-Line interface unit near/in the Fire Indicator Panel (FIP) or alarm system enclosure.
Two connection methods are shown:
- FIP with voltage-free relay outputs using an FP0740 End-of-Line Interface Unit.
- One ASE input pair is converted to relay connections for:
- Common Alarm
- Common Fault
- Common Isolate
- Relay outputs must be voltage-free relay/switch contacts.
- Relay common contacts must be electrically isolated from all other circuitry and from each other.
- Optocoupler outputs are stated as not compatible with the Centaur ASE.
- If Fault or Isolate relays are unavailable, the unused interface inputs are shorted together.
- One ASE input pair is converted to relay connections for:
- Alarm-only systems using an FP0743 Interface Unit.
- Used where only a common alarm output is available, such as a sprinkler system.
- The input is configured normally closed.
Wiring colour notes from guide
The OCR extracted these colour labels around the FP0740/FP0743 wiring diagrams:
- White twisted pair: ASE alarm system input wiring between ASE and End-of-Line interface.
- Red pair: alarm relay contacts.
- Yellow pair: fault relay contacts.
- Blue pair: isolate relay contacts.
For the alarm-only FP0743 interface, OCR shows:
- White pair: ASE input side.
- Red pair: N/C alarm relay side.
Cable / installation constraints
- The End-of-Line interface should be mounted within the alarm system/FIP enclosure.
- Only fire-rated cable attached to the white wires should be extended beyond the enclosure to the ASE.
- Remote input wiring can be extended up to 750 m using 1 mm² cable, with 30 Ω maximum total cable resistance.
- Input wiring must not run close to 240/415 VAC wiring for long distances because induced noise can cause false triggering.
- FP0740/FP0743 interface units are IP51 and should not be exposed to excessive moisture or heat.
Threshold voltages at ASE input terminals
The guide provides these approximate voltage states for normally-closed contact type input supervision:
Table
| ASE input voltage | State |
|---|---|
| 0.0 V | Short circuit |
| 0.38 V typical | Normal |
| 1.05 V typical | Isolate |
| 1.61 V typical | Fault |
| 1.98 V typical | Isolate + Fault |
| 2.17 V typical | Alarm |
| 2.44 V typical | Alarm + Isolate |
| 2.68 V typical | Alarm + Fault |
| 2.86 V typical | Alarm + Fault + Isolate |
| 5.0 V typical | Open circuit |
The OCR also showed threshold boundary values around these states; final firmware should use bands with margin rather than single exact thresholds.
Electrical specification extracted
- ASE supply voltage: 9.5 V min, 12/24 V typical, 29 V max.
- User target for our design: 12–24 VDC operating input.
- Alarm system input operating range: 0.0–5.0 V typical, up to 9.0 V max.
- Alarm input current at 0 V: approximately 4.2 mA.
- Normal current:
- Normally open: approximately 1.8 mA.
- Normally closed: approximately 4.0 mA.
- Power Fail input:
- Fault level: approximately 0.9 V.
- Normal level: approximately 3.0–29 V.
- Input current at 0 V: approximately 0.5 mA.
- Open collector outputs:
- On current sink up to 30 mA.
- Off voltage up to 29 V.
Design decision for our schematic
Implement each of the 8 inputs as an independent supervised analog input channel:
- Two-wire field/FAS input pair per channel.
- Protected current-limited excitation/source compatible with 5 V state measurement.
- Surge/ESD/noise filtering before ADC/comparator measurement.
- ADC measurement into STM32H757, with firmware decoding voltage bands for short, open, normal, alarm, fault, isolate, and combined states.
- Optional comparator/window-detect path for fail-safe hardware wake/fault detection.
- Per-channel terminal block labeling should support FAS1–FAS8 plus polarity.
Important caveat
The PDF OCR did not reliably extract the actual FP0740/FP0743 internal resistor values from the diagrams. We can still design the ASE input side from the published voltage bands and input-current behavior, but final compatibility requires confirming the resistor ladder values from the original diagram or measuring a reference interface unit.
Source
User direction
Extracted input architecture
Wiring colour notes from guide
Cable / installation constraints
Threshold voltages at ASE input terminals
Electrical specification extracted
Design decision for our schematic
Important caveat
