Category: Electronics

Pulsar V233-0060 stripped down

I bought a cheap Pulsar V233-0060 on eBay, you know, one that was advertised as “was working 10 years ago, just needs a battery”.

Of course if that was true, the seller would fit the battery and describe it as working and get lots more money for it.

Pulsar is one of Seiko’s brands, and this movement appears in Seiko branded watches.

Anyway, as it inevitably the case, it did not work.

External examination revealed that with a good battery, the 32kHz crystal was running, but no motor pulses. A further test with external turbo magnetic drive showed the motion works was working… so now pointing to a coil problem.
Continue reading Pulsar V233-0060 stripped down

Last update: 13th July, 2018, 6:43 PM

Inexpensive 4-20mA source – review

I bought a little 4-20mA source on eBay for under $10.

The device has a backlit LCD display, and a rotary encoder with steps of 0.05mA (or 0.3125% of 16mA). The current setting can be set as power on default by pressing the knob. It is supplied with a 250Ω resistor which could be used as a load resistor in projects delivering 500mV FSD.
Continue reading Inexpensive 4-20mA source – review

Last update: 5th May, 2018, 10:30 AM

Effect of shorting turns on a tapped air cored solenoid at RF #2

Effect of shorting turns on a tapped air cored solenoid at RF offers a simple model for estimating the effect of shorting turns on inductance (L) and Q.

A correspondent sent me a set of measurements he made of an air cored solenoid using a Q meter.

The coil was a 22t air solenoid of length 99.5mm and radius 31.56mm. Q of the whole coil (L12) was measured at 6MHz to be 475.

L and Q were estimated and measured with three different tapping points at one end of the coil.

Whilst the method described in the reference article does not attempt to estimate the effect of tapping where the unused turns are left open circuit, we might expect than when the unused section is a small part of the coil, that the effect is similar to that if the unused turns were not there.

A model as described in the reference article was constructed.

The notation is L1 is the used part of the coil, L2 is the unused part, L12 is the whole coil with no taps, Lms is measured L unused shorted, Lmo is measured L unused open, like wise for the Q subscripts.

Above, the model results There is quite good reconciliation with the predicted behaviour. Continue reading Effect of shorting turns on a tapped air cored solenoid at RF #2

Last update: 29th March, 2018, 11:53 AM

IoT water tank telemetry project – part 3

Battery trials

The project continues, albeit slowly.

Some inexpensive DC-DC boost converters have been very slow from China, though multiply source, they have not yet arrived.

An older module which was on hand has enabled progress of reliability and battery trials.

Above is the current prototype. The module on the white plug in cable is a 4-20mA simulator set to 20mA for maximum drain during battery trials. The module at upper right of the pic is a TP4056 batter charger and 1S protection board for the 2000mAh LiPo. The PV array (partially obscured) is capable of 80mA of charge current in full sunlight. The prototype includes a red LED drawing 1mA, an additional 24mAh load per day. Continue reading IoT water tank telemetry project – part 3

Last update: 18th March, 2018, 11:31 AM

Balancing a ceiling fan

I have a ceiling fan which has poor balance and is quite annoying on its high speed.

To solve the problem, I attached a flight controller board which I had on hand for this sort of purpose to the stationary spindle extension, and I have the associated configuration software installed for flying machines

Above, the OmnibusF4 v1 flight controller. Not a good flight controller for flying machines because of the silly pinout, but cheap (for that reason), about $20 on eBay. The flight controller contains a 3 axis gyro and accelerometer, the latter will be used here. Continue reading Balancing a ceiling fan

Last update: 11th March, 2018, 5:51 PM

Hobbyking 2500mAh 18650 LiIon cells (9210000181-0) initial capacity test

This article is documentation of a capacity test of 5 x Hobbyking 2500mAh 18650 LiIon cells (9210000181-0).

The cells were purchased on 26/02/2018 (~$7 + shipping) and received at about 30% charge. They were each charged in a XTAR VC2 Plus charger at 0.5A until charged.

The cells are 65mm long, and do not claim to contain protection modules which are prudent in some applications.

Each cell was then discharged at 1A (0.4C) to 2.8V, the discharge was captured.
Continue reading Hobbyking 2500mAh 18650 LiIon cells (9210000181-0) initial capacity test

Last update: 1st March, 2018, 8:32 AM

IoT water tank telemetry project – part 2

Calibration of the 4-20mA input

This article is a tutorial on calibrating the 4-20mA input which is designed for flexibility that is achieved through exploitation of the calibration.

The input device for this tutorial is a Pt100 RTD temperature sensor and inexpensive Chinese Pt100 – 4-20mA converter (loosely) calibrated for -50-150°. The Pt100, the converter, the load resistor, the divider resistors on the MCU board, and the MCu voltage reference all introduce error which is compensated in this end to end calibration procedure.

For this demonstration, two scenarios are measured:

  1. probe in still air whose temperature is captured with an accurate thermometer; and
  2. probe in boiling water whose temperature is calculated from known altitude and barometric pressure.

Another option would be to use a container of water filled with ice to obtain close to 0° for scenario 1… you don’t need a triple point cell for the end system stability and accuracy.

Temperature of boiling water

Using Calculate cooking time for soft boiled egg :

No, we are not boiling an egg, but the results include the temperature of the boiling water under current altitude and pressure. Continue reading IoT water tank telemetry project – part 2

Last update: 26th February, 2018, 12:43 PM

IoT water tank telemetry project – part 1

This is the first in a series of articles describing a simple maker / DIY IoT water tank telemetry system.

Design criteria

  • capture water depth, temperature and relative humidity;
  • IoT connectivity;
  • solar / battery powered;
  • wireless connection;
  • use existing inexpensive electronic modules.

Design choices made initially:

  • 4-20mA water pressure sensor for depth measurement;
  • ESP8266 Wemos D1 mini pro for the MCU and wireless elements;
  • NodeMCU / Lua software environment;
  • external antenna for improved WiFi range;
  • 6V 100mA PV array;
  • module with TP4056 batter charger and cell protection chip;
  • 2500mAh 18650 cell;
  • AM2320 temperature and humidity sensor;
  • bipolar transistor switch for boost converter;
  • Thingspeak RESTful interface for data accumulation and presentation.

Block diagram

Above is a block diagram showing the major system components. Almost all of the electronics is on easily obtained low cost electronic modules source from eBay, assembled on a Veroboard backplane. Continue reading IoT water tank telemetry project – part 1

Last update: 1st March, 2018, 11:33 AM