As the cable supplied with the panel is far too short, inflexible & does not even allow the cable gland on the terminal box to form a seal, I have replaced it with some high quality twin core guitar cable, with silicone insulation.
The cable is removable from the panel tail by means of a screwlock two pin connector.
On another note, I have noticed a side effect of fitting a switchmode regulator to the panel: it seems to have formed an MPPT-type regulator setup, as even in low light conditions, when the bare panel is outputting 18.5v at 50mA short circuit, with the switching regulator I can get a useable 13.25v at ~170mA.
This effect is increased in full light, where I can obtain 4.5A short circuit current & ~1.8A at 13.25v output.
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
Below is a link to the Eagle project archive for this. Includes schematic, board & gerber files.
Progress is finally starting on the power supply unit for the Pi, fitted into the same case style as the Pi itself, this is an 8Ah Li-Poly battery pack with built in voltage regulation.
Regulator Boards
Here are the regulators, fixed to the top of the enclosure. These provide the 12v & 5v power rails for the Pi unit, at a max 3A per rail.
Battery Pack
In the main body of the case the battery pack is fitted. This is made up of 4 3-cell Li-Poly RC battery packs, rated at 2Ah each. All wired in parallel this will provide a total of 8Ah at 12.6v when fully charged.
Powered Up
Here the regulators are powered up from a 13v supply for testing. I have discovered at full load these modules have very bad ripple, so I will be adding extra smoothing capacitors to the power rails to compensate for this.
I/O
Here are the connectors on the top of the unit, outputting the two power rails to the Pi & the DC barrel jack that will be used to charge the pack.
Having had a He-Ne laser tube for a while & the required power supply, it was time to mount the tube in a more sturdy manner. Above the tube is mounted with a pair of 32mm Terry Clips, with the power leads passing through the plastic top. The ballast resistor is built into the silicone rubber on the anode end of the tube. (Right).
Output power is about 1mW for this tube, which came from a supermarket barcode scanner from the 90’s. The tube is dated August 1993 & is manufactured by Aerotech.
Internals
Inside the box is the usual 2.2Ah 12v Li-Po battery pack & the brick type He-Ne laser supply. The small circuit in the centre is a switchmode converter that drops the 12v from the battery pack to the 5v required for the laser supply.
Here is an old chemical dosing system for industrial washing machines. These units are 4-pump models, with dual pumpheads. The motors are reversed to operate alternate pumps in the same head.
Label
From 2006, this is a fairly old unit, and made in the UK.
CPU Board
Main controller PCB, with interface to the power electronics via the ribbon cable, an external serial port for programming to it’s left. Powered by an ST microcontroller. The LCD is below this board.
PCU & Driver PCBs
Main power supply, sense input & motor driver boards. The PSU outputs +5v, +12v & +24v. The inputs on the lower left connect to the washing machine & trigger the pumps via the programming on the CPU. The motors are driven by L6202 H-Bridge drivers from ST.
Motor Assembly
Motor & gearbox assembly on the back of the pumphead. These are 24v DC units with 80RPM gearboxes.
UPDATE:
As it seems to be difficult to find, here is the user manual for this unit:
[download id=”5557″]
Here are the first set of mods & improvements to the RasPi Experiment board. Instead of the solder-point experiment space, I have added a standard mini-breadboard, even though it’s a little too long to fit on the board properly.
In the DIP breakout, is a MAX232 TTL-RS232 interface IC, useful for interfacing directly to the Pi’s UART, made available on the GPIO breakout. I will be hardwiring the MAX232 IC into the GPIO port, & fitting headers to the relevant pins on the IC breakout to make interfacing to the Pi easier.
All the MAX232 requires to operate are a 5v supply & 4 1µF capacitors.
The new TO220 device next to the breadboard is a TIP121 darlington power transistor.This is rated at 80v 5A continuous. Useful for driving large loads from a GPIO output.
After seeing these on eBay for £8.99 I thought it might be a good deal – interfacing with the RasPi’s GPIO & it has built in power supplies.
As a kit, it was very easy to assemble, the PCB quality is high, and is a fairly good design. It worked first time, the regulators hold the rails at the right voltages.
However there are some issues with this board that bug me.
The documentation for the kit is *AWFUL*. No mention of the regulators on the parts list & which goes where – I had to carefully examine the schematics to find out those details.
The 4x 1N1007 diodes required weren’t even included in the kit! Luckily I had some 1N4148 high speed diodes lying around & even though they’re rated for 200mA continuous rather than the specified part’s 1A rating, the lack of heatsinking on the regulators wouldn’t allow use anywhere near 1A, so this isn’t much of a problem.
Component numbering on the silkscreen isn’t consistent – it jumps from R3 straight to R6! These issues could be slightly confusing for the novice builder, and considering the demographic of the RasPi, could be seen as big issues.
On the far left of the board are the 5v & 3.3v regulators, well placed on the edge of the board in case a heatsink may be required in the future. However the LM317 adjustable regulator is stuck right in the middle of the PCB – no chance of being able to fit a heatsink, & the device itself seems incredibly cheap – the heatsink tab on the back of the TO-220 is the thinnest I have ever seen. Not the usual 2-3mm thick copper of the 5v & 3.3v parts – but barely more than a mm thick, so it’s not going to be able to cope with much power dissipation without overheating quickly.
As the adjustable rail can go between ~2.5v – 10v, at the low end of the range the power dissipation is going to shoot through the roof.
The GPIO connector – this could have been done the other way, at the moment the ribbon cable has to be twisted to get both the Pi & the GPIO board the same way up. Just a slight fail there. See the image below
Plugged In
The power rails are not isolated out of the box – there is no connection between the 5v & 3.3v rails & the Pi’s GPIO, but the GND connections are linked together on the board.
Getting the ribbon cable through the hole in the ModMyPi case was a bit of a faff – the connector is too big! I had to squeeze the connector through at a 45° angle. The case is also remarkably tight around the connector once it’s fitted to the board – clearly the designers of the case didn’t test the an IDC connector in the case before making them!
Everything does fit though, after a little modification.
All Cased Up
Here is the unit all built up with the case. The top cover just about fits with the IDC connector on the GPIO header.
More to come once I get some time to do some interfacing!
Just a quickie to note down the current progress of another project – Ultracapacitors.
Pictured right is a bank of 6 2.5v 2600F Maxwell Boostcaps, for a total of 15v at 433.333F. A total energy storage of 48.7kJ.
Coming soon will be the inclusion of charge balancing, using Zener diodes & integrating a DC-DC converter on the output to hold the bank voltage at 12v when being used.
This is a device to use an IDE or SATA interface drive via a USB connection. Here is the front of the device, IDE interface at the bottom, 2.5″ form factor.
PCB Top
PCB removed from the casing. USB cable exits the top, 12v DC power jack to the left.
SATA interface below the DC Jack.
Molex connector below SATA is the power output for the drive in use. This unit has a built in 5v regulator.
PCB Bottom
Bottom of the PCB showing the interface IC.
Drive Adaptor
Adaptor to plug into the 44-pin 2.5″ form factor IDE interface on the adaptor, converts to standard 40-pin 3.5″ IDE.
Power Cable
Power pigtail with standard Molex & SATA power plugs.
This is an old CO alarm, which was totally dead, having been connected to the wrong PSU.
Here is the front of the unit, with the Test button & indicator LEDs.
Overview
Front of the PCB, 3 1.5v cells powered the unit, Piezo sounder & sensor cell in the centre of the board.
A quick post documenting a DPSS laser module i salvaged from a disco scanner. Estimated output ~80mW
Diode Connection
Connection to the 808nm pump diode on the back of the module. There is a protection diode soldered across the diode pins. (Not visible). Note heatsinking of the module.
Driver PCB
Driver PCB. This module was originally 240v AC powered, with a transformer mounted on the PCB with a built in rectifier & filter capacitor. I converted it to 5v operation. Emission LED on PCB.
To help make my system more efficient, a pair of switching regulators has been fitted, the one shown above is a Texas Instruments PTN78060 switchmode regulator module, which provides a 7.5v rail from the main 12v battery pack.
A Lot like the LM317 & similar linear regulators, these modules require a single program resistor to set the output voltage, but are much more efficient, around the 94% mark at the settings used here.
The 7.5v rail supplies the LM317 constant current circuit in the laser diode driver subsection. This increases efficiency by taking some voltage drop away from the LM317.
5v Regulator
The 7.5v rail also provides power to this Texas Instruments PTH08000 switchmode regulator module, providing the 5v rail for the USB port power.
This is detailing my portable multi-purpose power pack of my own design. Here is an overview, mainly showing the 4Ah 12v Ni-Cd battery pack.
Front Panel Right
Panel Features – Bottom: Car cigar lighter socket, main power keyswitch. Top: LED toggle switch, provision for upcoming laser project, Red main Power LED, 7A circuit breaker.
Front Panel Left
Top: Toggle switch serving post terminals, USB Port.
Post terminals supply unregulated 12v for external gadgets. USB port is standard 5v regulated for charging phones, PDAs etc.
Bottom: Pair of XLR connectors for external LED lights. Switches on their right control power & the knob controls brightness.
Additions are being made to this all the time, the latest being a 2W laser diode driver. Update to come soon!
This is an old USB 1.1 hub that was recently retired from service on some servers. Top of the unit visible here.
Bottom Label
Bottom label shows that this is a model F5U021 hub, a rather old unit.
PCB Front
PCB is here removed from the casing, Indicator LEDs along the bottom edge of the board, power supply is on the left. Connectors on the top edge are external power, USB host, & the 4 USB outputs. Yellow devices are polyswitch fuses for the 500mA at 5v each port must supply.
USB Hub IC
This is the USB Hub Controller IC, which is a Texas Instruments TUSB2046B device. Power filter capacitors next to the USB ports are visible here also, along with 2 of the polyswitches.
Power Supply
The power supply section of the unit, which supplies regulated 5v to the ports, while supplying regulated 3.3v to the hub controller IC. Large TO-220 IC is the 5v regulator. Smaller IC just under the power selector switch is the 3.3v regulator for the hub IC. The switch selects between Host powered or external power for the hub.
This is a device designed to reset Epson brand ink cartridges that are reportedly out of ink, so they again report full to the printer Here is the front of the unit, with the guide for attaching to a cartridge.
PCB Back
Back of the device removed. 3 button cells provide power to the PCB. Indicator LED sticks out of the top of the device for reset confirmation.
Row of pads on far left edge of the PCB are presumably a programming header for the uC on the other side of the board.
PCB Front
Here is the front of the PCB, main feature being the grid of pogo pins to connect to the cartridge chip. IC on lower right of that is a MSP430F2131 uController, a Texas Instruments part.
The IC directly to the left of the pogo pin bed is a voltage regulator, to step down the ~4.5v of the batteries down to the ~3.3v that the uC requires.
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