Casio fx-61F Electronic Formula 27 Calculator

My old trusty Casio fx-61F “Electric formula 27” calculator is still going strong and gets regular use. It was bought in a sale from Maplin Electronics UK, some time in the 90s from a bargain bin as I recall. Why is it so special? Its a calculator specifically designed for electrical and electronic engineering. I don’t know Read more about Casio fx-61F Electronic Formula 27 Calculator[…]

Ticket To My Heart – Admit One

With Valentine’s Day approaching I thought I would share this design for a custom gift which I made. It’s a Printed Circuit Board (PCB) in the guise of a cinema ticket inscribed with the words Ticket to my heart, admit one. I had versions produced at elecrow and at PCBs.io, both of whom produced fine Read more about Ticket To My Heart – Admit One[…]

Infra-red remote control tester

Is the TV broken, has the TV software stopped responding or is it just that the remote controls batteries have gone flat again? This little paper circuit will test if your remote control signal is being sent and therefore whether the batteries are still working. You can easily fit this one inside your logbook for Read more about Infra-red remote control tester[…]

BLE serial hub to WiFi and Blynk visualisation app

So that I can continuously post environmental data to the Blynk cloud service from my Bluetooth environmental monitor, I’ve implemented a simple design using a Keyes HM-10 Bluetooth 4.0 module and a Wemos D1 mini WiFi device as a Bluetooth hub and internet gateway. If you are not familiar with the Wemos D1 Mini. It’s Read more about BLE serial hub to WiFi and Blynk visualisation app[…]

Digital multimeter calibration for voltage, resistance and current

I got a little carried away with this one! I have an old multi-meter whose calibration was unknown. Surely an accurate voltage reference would help with that. After spending somewhere around £80.00 designing and building a calibrator for my cheapo old multi-meter i feel I’ve given this project more than it needed:-)     There Read more about Digital multimeter calibration for voltage, resistance and current[…]

LED lamp dimmer with a 555 timer and comparator

I wanted a simple bedside lamp with a continuously variable brightness. Something I could read from whilst also being able to dim the lamp in an analogue manner to a level where it could be left turned on over night so that I could see the baby but not wake him in his Moses basket. Read more about LED lamp dimmer with a 555 timer and comparator[…]

Environmental Monitor Node Using HM-10 Bluetooth LE

Knowing the babies room temperature has become a bit of an obsession. When the temperature changes you need to make sure baby doesn’t wake up due to the cold or more serious still to make sure they don’t get too hot. SIDS is a worry in the back of every new parents mind. Not that Read more about Environmental Monitor Node Using HM-10 Bluetooth LE[…]