Radio Remi guidesA technician must decide whether ideal average current is safe before changing advertising interval on the real device. The result is unresolved until the rule and units are checked. Predict the direction first.
See the relationship before changing it
The figure reads from left to right. The blue card is advertising interval. The middle card applies this page's rule. The green card is ideal average current. Walk the arrows once: set the input, apply the rule, then read the result with its unit.
The retained audit below checks several chapter fixtures. This model keeps those stated values fixed and changes only advertising interval, so the numeric fixture does not switch without explanation.
Derive the baseline in four named moves
- 1
Name the input. The chapter baseline is 1 s.
- 2
Name the relationship. average = 2 uA sleep + 4.8582 uA s / interval
- 3
Substitute with units. 2 + 4.8582 / 1 = 6.858 uA
- 4
Read the result. Keep the unit beside the value. Use it only inside the technical boundary on this page.
Predict, then change advertising interval
Try Predict the direction of average = 2 uA sleep + 4.8582 uA s / interval. Test another advertising interval, then compare ideal average current.
Observe Longer intervals spread the fixed advertising event over more sleep time. Reset advertising interval to 1 and compare ideal average current.
Explain Longer intervals spread the fixed advertising event over more sleep time.
Check yourself
What should you do before trusting a moved-control result?
What does this small model leave out?
1. Average current is area under pulses
A short current pulse spends charge for only its duration. Count the pulses, multiply current by time, and then add the sleep current that runs between them. Battery capacity must be derated before dividing by that daily cost.
2. Name every algebra move
Count daily eventsNday=86,400/Tinterval.
Add event and sleep energyEday=Nday VIactive tevent+VIsleep×86,400.
Divide the usable budgetlife=Qnominal fderate V×3600/Eday.
3. Antenna loss can change the current term
If enclosure detuning removes antenna gain, holding the same EIRP needs more conducted power. That can increase active current even when firmware timing is unchanged.
4. Try one controlled change
TryLengthen only the advertising interval. The event shape, sleep current, and cell stay fixed.
ObserveAt 1 s, 86,400 events cost about 1.26 J/day; sleep adds 0.518 J/day. The 1900.8 J budget gives roughly 1,068 days or 2.93 years.
ExplainLonger intervals reduce the pulse term but not the sleep term. Doubling active current after antenna detuning raises the 1 s total to about 3.04 J/day and lowers the bound to 1.71 years.
The 5.4 mA, 0.9 ms event and cell values form a catalog-typical illustration.
- Advertising event
- Changes with payload, channels, and retries
- Sleep and connection load
- Depend on the complete firmware schedule
- Usable cell energy
- Depends on temperature, age, passivation, and cutoff
Measure current waveforms and the selected power path before predicting service life.
5. Reproduce the chapter values
At 1 s, active energy is 0.0054×3.0×0.0009×86,400=1.26 J/day and active charge is 0.117 mAh/day. Sleep is 2 µA×3.0 V×86,400=0.518 J/day and 0.048 mAh/day, so total energy is 1.78 J/day. Usable energy is 220 mAh×0.8×3.0 V×3.6=1900.8 J. Exact unrounded inputs give about 1,069 days; the chapter’s rounded 1.78 J/day gives 1,068 days, and both round to 2.93 years. Doubling active current gives 3.04 J/day and about 626 days=1.71 years.
6. Carry the evidence forward
Capture interval and payload, event and connection traces, sleep current, retries, scan responses, transmit setting, antenna efficiency, enclosure state, cell lot, temperature, cutoff, and field lifetime trend.
7. Check yourself
Why does a longer interval not remove all drain?
Where does 1900.8 J come from?
Why can antenna detuning reduce life?
The page reproduces the chapter's rounded advertising budget and shows the exact arithmetic.
- 1,900.8 J
- Exact derated teaching budget
- 1.78 J per day
- Rounded chapter illustration
- 1,068 versus 1,069 days
- Rounding difference, both about 2.93 years
Neither result includes every real device load or cell limitation.