Sensor turn on time

We have had an issue with units automaticly waking from sleep when using code that switch off the Hall sensor when in sleep to save power. Today I took some time to investigate this instead of just using a workaround (not disabling the sensor while sleeping).

I had an idea that it might be that it takes some time for the sensor to output the correct value after getting power. This turned out to be correct but not in the way I expected. When the circuit is fed power at over about 3.1 V there is no delay for reading correct state of sensor. When the voltage drops to 3.1 V or under on the other hand it takes about 70 ms for it to output correct value.

In the below figures, C1 is the level at the Vs pin of the Hall sensor and C2 is at the output. Decreasing the voltage down all the way to 2.4 V (minimum working voltage for the sensor) there is no change in time to turn on.

Under threshold

Over threshold

Final prototypes

The PCBs for the final prototypes have arrived and been assembled, here are some picutres. Some footprints for parts need minor adjustment but otherwise this should be the final version. The circuit measures 21 mm in diameter and 2.5 mm at the thickest part (this will be reduced by 0.2 mm for the production version due to changing from 0.6 mm thick PCB to 0.4 mm thick).

Protoype size


Status update

We are starting to spread the word about Grimlight on various forums and sites. We will update our homepage adding better quality photos and videos the coming week and we need your help in spreading the word!

The final set of prototypes will hopefully be in our hands soon and the dimensions will be smaller than ever. We look forward to sharing ideas and pictures with modelers, wargamers, larpers and anyone in need of our unique miniature lighting solution.

Would you like to get your hands on one of our prototypes? Anyone who signs up for our newsletter before October 1st will have the chance to get a prototype. We will draw a lucky winner out of all our newsletter subscribers on October 1st who will have a prototype sent to them by mail.

Battery test

During the last week there have been some testing of power consumption for the circuits. Voltage over the battery driving the circuit was recorded while one LED was constantly glowing and when in standby (different batteries).

Battery test

With one LED on the battery lasted about 14 hours before the voltage dropped so it was too low to drive the LED. In standby (battery in circuit but everything switched to low power mode, battery not physically disconnected as there is no switch) the voltage dropped about 0.01 V during the first 24 hours and then stabilized. Fitting a line to the drop during the last 100 hours measured indicates that it would take about 400 days to drop from 2.99 V to 2.90 V. Worth noting is that with one LED on it took about 5 minutes to drop under 2.8 V.

This was tested with CR1220 batteries and not CR1216 because we have not been able to find any good holder for that type of battery. The holder on the prototypes can take CR1216 up to CR1225, but CR1216 has a bad fit an don’t make a very good connection. Currently looking into sourcing better battery holders.


Magnet control switch to indicate firing.