PCB

Marine Potable Water Management System

LCD Panel

LCD Panel

Having two separate water tanks on nb Tanya Louise, with individual pumps, meant that monitoring water levels in tanks & keeping them topped up without emptying & having to reprime pumps every time was a hassle.
To this end I have designed & built this device, to monitor water usage from the individual tanks & automatically switch over when the tank in use nears empty, alerting the user in the process so the empty tanks can be refilled.

Based around an ATMega328, the unit reads a pair of sensors, fitted into the suction line of each pump from the tanks. The calculated flow is displayed on the 20×4 LCD, & logged to EEPROM, in case of power failure.

Water Flow Sensor

Water Flow Sensor

When the tank in use reaches a preset number of litres flowed, (currently hardcoded, but user input will be implemented soon), the pump is disabled & the other tank pump is enabled. This is also indicated on the display by the arrow to the left of the flow register. Tank switching is alerted by the built in beeper.
It is also possible to manually select a tank to use, & disable automatic operation.
Resetting the individual tank registers is done by a pair of pushbuttons, the total flow register is non-resettable, unless a hard reset is performed to clear the onboard EEPROM.

Main PCB

Main PCB

View of the main PCB is above, with the central Arduino Pro Mini module hosting the backend code. 12-24v power input, sensor input & 5v sensor power output is on the connectors on the left, while the pair of pump outputs is on the bottom right, switched by a pair of IRFZ44N logic-level MOSFETS. Onboard 5v power for the logic is provided by the LM7805 top right.

Code & PCB design is still under development, but I will most likely post the design files & Arduino sketch once some more polishing has been done.

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Wednesday, May 14th, 2014 Arduino, Personal Project Comments Off

Flyback Driver Kits Now Available For Sale

Flyback Driver Kit

Flyback Driver Kit

As I have some spare boards & the capability to etch plenty more, I figured I could supply DIY kits of my Flyback Driver circuit.

This kit & the associated flyback transformers are capable of producing very high voltages which can be hazardous!

Kit will include both a custom etched PCB & all the components required to build a working circuit.

Price is £18 with free shipping to anywhere within the UK

NOTE: A heatsink for the main switching MOSFET is required. This is supplied separately to reduce costs for hobbyists that already have such things lying around. If you require a heatsink, please add the heatsink option to your cart when purchasing. Provision is also made on the PCB for a fan, if being run at high power.

Flyback Driver Kit:


Heatsink:

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Friday, December 13th, 2013 Hacks, Personal Project, Randoms Comments Off

555 Flyback Driver

Board Layout

Board Layout

Here is a simple 555 timer based flyback transformer driver, with the PCB designed by myself for some HV experiments. Above is the Eagle CAD board layout.

The 555 timer is in astable mode, generating a frequency from about 22kHz to 55kHz, depending on the position of the potentiometer. The variable frequency is to allow the circuit to be tuned to the resonant frequency of the flyback transformer in use.

This is switched through a pair of buffer transistors into a large STW45NM60 MOSFET, rated at 650v 45A.

Input power is 15-30v DC, as the oscillator circuit is fed from an independent LM7812 linear supply.

Provision is also made on the PCB for attaching a 12v fan to cool the MOSFET & linear regulator.

Initial Board

Initial Board

Board initially built, with the heatsink on the linear regulator fitted. I used a panel mount potentiometer in this case as I had no multiturn 47K pots in stock.

PCB Traces

PCB Traces

Bottom of the PCB. The main current carrying traces have been bulked up with copper wire to help carry the potentially high currents on the MOSFET while driving a large transformer.
This board was etched using the no-peel toner transfer method, using parchement paper as the transfer medium.

MOSFET Heatsinked

MOSFET Heatsinked

Main MOSFET now fitted with a surplus heatsink from an old switchmode power supply. A Fan could be fitted to the top of this sink to cope with higher power levels.

Gate Drive Waveform

Gate Drive Waveform

This is the gate drive waveform while a transformer is connected, the primary is causing some ringing on the oscillator. The waveform without an attached load is a much cleaner square wave.

Flyback Secondary Waveform

Flyback Secondary Waveform

I obtained a waveform of the flyback secondary output by capacitively coupling the oscilloscope probe through the insulation of the HT wire. The pulses of HV can be seen with the decaying ringing of the transformer between cycles.

Corona Discharge

Corona Discharge

Arc Discharge

Arc Discharge

Corona & arc discharges at 12v input voltage.

Download the Eagle schematic files here: Flyback Driver Eagle Files (134)

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Tuesday, December 3rd, 2013 Personal Project, Randoms Comments Off

Rio LAHS4 Salon Laser Hair Remover

Unit Overview

Unit Overview

Here is a home laser hair removal unit, a Rio LAHS4. Shown above is the system overview, with the laser wand & the user controls.

Main PCB Top

Main PCB Top

Main base unit popped open reveals the main PCB, with the central processor, a PIC16F628A.

Main PCB Bottom

Main PCB Bottom

Other side of the PCB is mainly populated with power supply & filtering for the logic sections.

Wand PCB

Wand PCB

Cracking open the laser wand reveals a stacked pair of PCBs, a main laser controller & the capacitive sensor PCB. This capacitive sensor connects to a pair of pins on the laser head & prevents operation if the unit is not held firmly against the skin.

Diode Module

Diode Module

Front of the laser diode module with the movable lens, on a pair of voice coil actuators. Very similar to the lens positioner used in any CD/DVD player pickup assembly.
The diode in this unit is an 808nm chip, with power in the 300-600mW range most likely.

Diode Module Rear

Diode Module Rear

Rear of the diode module, with the connections to the diode itself & the voice coil positioner for the lens.

Wand PCB Top

Wand PCB Top

Other side of the wand PCB, showing the capacitive sensor board on top of the main controller board. There is another CPU on the board here, which most likely communicates with the main processor in the base through a serial connection.

 

 

 

 

 

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Tuesday, October 1st, 2013 Consumer Gear Comments Off

Wearable Raspberry Pi – Some Adjustments

USB Hub

USB Hub

As the first USB hub I was using was certainly not stable – it would not enumerate between boots & to get it working again would require waiting around 12 hours before applying power, it has been replaced. This is a cheapie eBay USB hub, of the type shown below.

These hubs are fantastic for hobbyists, as the connections for power & data are broken out on the internal PCB into a very convenient row of pads, perfect for integration into many projects.

Breakout Hub

Breakout Hub

I now have two internal spare USB ports, for the inbuilt keyboard/mouse receiver & the GPS receiver I plan to integrate into the build.

These hubs are also made in 7-port versions, however I am not sure if these have the same kind of breakout board internally. As they have the same cable layout, I would assume so.

 

Connector Panel

Connector Panel

Here is a closeup of the back of the connectors, showing a couple of additions.

I have added a pair of 470µF capacitors across the power rails, to further smooth out the ripple in the switching power supply, as I was having noise issues on the display.

Also, there is a new reset button added between the main interface connectors, which will be wired into the pair of pads that the Raspberry Pi has to reset the CPU.
This can be used as a power switch in the event the Pi is powered down when not in use & also to reset the unit if it becomes unresponsive.

 

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Monday, April 22nd, 2013 Personal Project, RasPi Comments Off

Ultracapacitor Charge Balancing

Balancer

Balancer

I have finally  got round to designing the balancing circuitry for my ultracapacitor banks, which have a total voltage of 15v when fully charged. The 2600F capacitors have a max working voltage of 2.5v each, so to ensure reliable operation, balancing is required to make sure that each capacitor is charged fully.

The circuit above is a simple shunt regulator, which uses a 2.2v zener diode to regulate the voltage across the capacitor.

A 10W 1Ω resistor is connected to the BALLAST header, while the capacitor is connected across the INPUT. Once the voltage on the capacitor reaches 2.6v, the MOSFET begins to conduct, the 1Ω resistor limiting current to ~2.6A.

Each capacitor in the series string requires one of these connected across it.

PCB

PCB

Below is a link to the Eagle project archive for this. Includes schematic, board & gerber files.

Ultracapacitor Balancer Project Files (264)

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Thursday, April 11th, 2013 Personal Project, Randoms Comments Off
Creative Commons Licence
Inside Electronics by Ben Thomson is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.
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