LightSafer User Guide

LightSafer is a tiny, silent hotel safe alarm - read all about it on the LightSafer home page.


  1. Turning on
  2. Arming
  3. Armed
  4. Alarm
  5. Notes
  6. Changing the PIN

Turning on

With LightSafer turned off, press the joystick in for a couple of seconds. Three green LEDs will light.

The LEDs will then indicate the battery level, from low (one LED on the left) to high (all 6 LEDs lit). You can expect a good few hours' battery life in the armed state when only one LED is lit. If no LEDs illuminate then the battery should be replaced. The image below shows 5 LEDs lit, so this LightSafer has just less than full battery level.

LightSafer battery level

LightSafer is now in a standby state with one green LED lit. It will turn back off after 30 seconds of inactivity, to preserve battery life.

LightSafer standby state


When in the standby state, arm the device by pressing the joystick in once. The red and green LEDs light:

LightSafer arming

You now have 20 seconds to put LightSafer in your safe (or other dark place you want to protect!). Press the joystick in again before the end of the 20 seconds to cancel the arming state and go back to standby.


Once LightSafer is armed, the red 'armed' LED will briefly illuminate, before all LEDs turn off, saving power whilst armed. You won't see this happen because you'll have closed up your safe, or zipped your bag up.


As soon as LightSafer sees a small amount of light, it will light up the red and green LEDs and request your PIN - you now have 30 seconds, or 3 attempts to input the correct PIN. To enter the pin, use the up (1), right (2), down (3) and left (4) directions on the joystick. For example, to enter the default PIN of 12341234, enter up, right, down, left, up, right, down, left.

LightSafer - enter PIN

If you get the PIN wrong, the following LEDs light:

LightSafer wrong PIN

You then get another go at entering the correct PIN. If you get the PIN right then you'll end up back in the standby state, but if you use all three attempts or take more than 30 seconds then LightSafer will enter the alarm state.


The alarm state looks like this:

LightSafer wrong PIN

You will be in this state if LightSafer had previously been armed, then triggered by a small amount of light, then the correct PIN wasn't entered. You can work out how long ago the alarm was set off by briefly pressing the joystick in. The right red LED will flash once for each 15 minute period since the alarm was triggered. For example if it were triggered an hour ago, the LED would flash 4 times.

To get LightSafer out of the alarm state, press and hold the joystick for a few seconds, then enter the correct PIN and you'll be back in the standby state.


  1. The state is preserved in the non-volatile EEPROM. Once the alarm has been triggered, there is no way that it can be reset without either entering the correct PIN, or reflashing the PIC (and therefore resetting the PIN back to 12341234).
  2. If you've forgotten the PIN then reflashing the PIC is the only way to make LightSafer usable again. Your current PIN will be lost.

Changing the PIN

You can change the PIN from the default (12341234) using the following method:

  1. Ensure LightSafer is either turned off or in standby (i.e. not armed or alarming)
  2. Remove the CR2032 battery
  3. Whilst holding up on the joystick, insert the battery. The LEDs will light:

    LightSafer PIN change

  4. Enter your current PIN. If you get the PIN wrong then LightSafer will enter the alarm state. If you get the PIN right then the following LEDs will light:

    LightSafer PIN change again

  5. Enter the new PIN, the following LEDs will light:

    LightSafer PIN change reenter PIN

  6. Re-enter the new PIN. If it matches then all three green LEDs will flash twice, indicating that the PIN has been changed successfully. If the green LEDs don't flash then the PIN hasn't been changed. Either way, you will go back to the standby state.
  7. PINs must be exactly 8 digits in length.

Andy C
May 2019