timing – Experimental Engineering

Posted on March 15, 2018March 15, 2018 by The Engineer — Leave a comment

Raspberry Pi 3 Model B+ Initial Tests & Benchmarks

Yesterday, the Raspberry Pi community got a nice surprise – a new Pi! This one has some improved features over the previous RPi 3 Model B:

Improved CPU – 64-Bit 1.4GHz Quad-Core BCM2837B0
Improved WiFi – Dual Band 802.11b/g/n/ac. This is now under a shield on the top of the board.
Improved Ethernet – The USB/Ethernet IC has been replaced with a LAN7515, supporting gigabit ethernet. The backhaul is still over USB2 though, so this would max out at about 300Mbit/s
PoE Support – There’s a new 4-pin header, and a matching HAT for power over ethernet support.

The USB/LAN Controller is now a BGA package, supporting gigabit ethernet. The USB connections are still USB2 though, limiting total bandwidth. This shouldn’t be much of an issue though, since anything over the 100Mbit connection we’ve had previously is an improvement.

The CPU now has a metal heatspreader on top of the die, no doubt to help with cooling under heavy loads. As far as I know, it’s still the same silicon under the hood though. The WiFi radio is under the shielding can to the top left, with the PCB trace antenna down the left edge of the board.

The power supplies are handled on this new Pi by the MaxLinear MxL7704, from what I can tell from MaxLinear’s page, it seems to be somewhat of a collaborative effort to find something that would do the best job, since they apparently worked with the Foundation to get this one right. This IC apparently includes four synchronous step-down buck regulators that provide system, memory, I/O and core power from 1.5A to 4A. An on-board 100mA LDO provides clean 1.5V to 3.6V power for analog sub-systems. This PMIC utilizes a conditional sequencing state machine that is flexible enough to meet the requirements of virtually any processor.

The bottom of the PCB has the Elpida 1GB RAM package, which is LPDDR2, along with the MicroSD slot.

A quick benchmark running Raspbian Lite & a SanDisk Ultra 32GB Class 10 SD card gives some nice results:

Raspberry Pi Benchmark Test
Author: AikonCWD
Version: 3.0

temp=45.1'C
arm_freq=1400
core_freq=400
sdram_freq=500
gpu_freq=300
sd_clock=50.000 MHz

Running InternetSpeed test...
Ping: 45.278 ms
Download: 151.50 Mbit/s
Upload: 9.52 Mbit/s

Running CPU test...
 total time: 11.3003s
 min: 4.48ms
 avg: 4.51ms
 max: 44.50ms
temp=56.4'C

Running THREADS test...
 total time: 10.2161s
 min: 3.94ms
 avg: 4.08ms
 max: 21.49ms
temp=59.6'C

Running MEMORY test...
Operations performed: 3145728 (2418384.67 ops/sec)
3072.00 MB transferred (2361.70 MB/sec)
 total time: 1.3008s
 min: 0.00ms
 avg: 0.00ms
 max: 9.99ms
temp=60.7'C

Running HDPARM test...
 Timing buffered disk reads:  66 MB in  3.01 seconds =  21.91 MB/sec
temp=51.5'C

Running DD WRITE test...
536870912 bytes (537 MB, 512 MiB) copied, 34.6011 s, 15.5 MB/s
temp=46.7'C

Running DD READ test...
536870912 bytes (537 MB, 512 MiB) copied, 23.5404 s, 22.8 MB/s
temp=45.6'C

AikonCWD's rpi-benchmark completed!

Posted on September 27, 2016 by The Engineer — Leave a comment

Inductive Hour Counter / Tachometer – Petrol Engines

As one of my current projects involves a small petrol engine – a Honda GX35 clone, I figured an hour counter would be very handy to keep an eye on service intervals. (More to come on the engine itself later on). I found a device that would suit my needs on good old eBay.

These engine monitors are pretty cheap, at about £4. The sensing is done by a single heat-resistant silicone wire, that wraps around the HT lead to the spark plug. The unit can be set for different firing intervals via the buttons. In the case of most single-cylinder 4-stroke engines, the spark plug fires on every revolution – wasted-spark ignition. This simplifies the ignition system greatly, by not requiring the timing signal be driven from 1/2 crankshaft speed. The second “wasted” spark fires into the exhaust stroke, so has no effect.

The back cover is lightly glued into place with a drop of cyanoacrylate in opposite corners, but easily pops off. The power is supplied by a soldered-in 3v Lithium cell. The main microcontroller has no number laser etched on to it at all – it appears it skipped the marking machine.

The input from the sensing wire comes in through a coupling capacitor & is amplified by a transistor. It’s then fed into a 74HC00D Quad 2-Input NAND gate, before being fed into the microcontroller.

The pickup wire is simply wound around the spark plug lead. I’ve held it in position here with some heatshrink tubing. Heat in this area shouldn’t be an issue as it’s directly in the airflow from the flywheel fan.

Posted on September 30, 2014October 6, 2014 by The Engineer — Leave a comment

HPI Nitrostar F4.6 Ignition Conversion

As there was no other online example of someone converting a glow/nitro car engine onto CDI ignition, I thought I would document the highlights here.
The engine is currently still running on glow fuel, but when the required fuel lines arrive I will be attempting the switch over to 2-Stroke petrol mix. This should definitely save on fuel costs.

The engine in this case is a HPI NitroStar F4.6 nitro engine, from a HPI Savage X monster truck.

Above is the converted engine with it’s timing sensor. As The installation of this was pretty much standard, a complete strip down of the engine was required to allow the drilling & tapping of the two M3x0.5 holes to mount the sensor bracket to. The front crankshaft bearing has to be drifted out of the crankcase for this to be possible.

Detail of the ignition hall sensor. The bracket has to be modified to allow the sensor to face the magnet in the flywheel. Unlike on an Aero engine, where the magnet would be on the outside edge of the prop driver hub, in this case the hole was drilled in the face of the flywheel near the edge & the magnet pressed in. The Hall sensor is glued to the modified bracket with the leads bent to position the smaller face towards the back of the flywheel.
The clearance from the magnet to sensor is approx. 4mm.

Detail of the magnet pressed into the flywheel. A 3.9mm hole was drilled from the back face, approx 2mm from the edge, & the magnet pressed into place with gentle taps from a mallet & drift, as I had no vice to hand.
Initial timing was a little fiddly due to the flywheel only being held on with a nut & tapered sleeve, so a timing mark can be made inside the rear of the crankcase, across the crank throw & case to mark the 28 degree BTDC point, the flywheel is then adjusted to make the ignition fire at this point, before carefully tightening the flywheel retaining nut to ensure no relative movement occurs.
The slots in the sensor bracket allow several degrees of movement to fine adjust the timing point once this rough location has been achieved.

Definitely the tiniest spark plug I’ve ever seen, about an inch long. Some trouble may be encountered with this on some engines – the electrodes stick out about 2mm further into the combustion chamber than a standard glow plug does. This causes the ground electrode to hit the top of the piston crown. (This happens on the HPI NitroStar 3.5 engine). The addition of another copper washer under the plug before tightening should cure this problem.

Ignition module. Due to the depth of the plug in the heatsink head on these engines, I will have to modify the plug cap to straighten it out, as it will not fit in this configuration.
However, ignition modules are available from HobbyKing with straight plug caps, this makes modification unnecessary

The ignition & components used on this system were obtained from JustEngines.

Posted on February 2, 2012 by The Engineer — Leave a comment

Zebra P330i Card Printer

This is the teardown of a Zebra P330i plastic card printer, used for creating ID cards, membership cards, employee cards, etc. I got this as a faulty unit, which I will detail later on.
This printer supports printing on plastic cards from 1-30mils thick, using dye sublimation & thermal transfer type printing methods. Interfaces supplied are USB & Ethernet. The unit also has the capability to be fitted with a mag stripe encoder & a smart card encoder, for extra cost.

On the left here is the print engine open, the blue cartridge on the right is a cleaning unit, using an adhesive roller to remove any dirt from the incoming card stock.
This is extremely important on a dye sublimation based printing engine as any dirt on the cards will cause printing problems.

Here on the right is the card feeder unit, stocked with cards. This can take up to 100 cards from the factory.
The blue lever on the left is used to set the card thickness being used, to prevent misfeeds. There is a rubber gate in the intake port of the printer which is moved by this lever to stop any more than a single card from being fed into the print engine at any one time.

Here is the empty card feeder, showing the rubber conveyor belt. This unit was in fact the problem with the printer, the drive belt from the DC motor under this unit was stripped, preventing the cards from feeding into the printer.

Here is a closeup of the print head assembly. The brown/black stripe along the edge is the row of thin-film heating elements. This is a 300DPI head.

This is under the print head, the black roller on the left is the platen roller, which supports the card during printing. The spool in the center of the picture is the supply spool for the dye ribbon.
In the front of the black bar in the bottom center, is a two-colour sensor, used to locate the ribbon at the start of the Yellow panel to begin printing.

Inside the top cover is the indicator LCD, the back of which is pictured right.
This is a 16×1 character LCD from Hantronix. This unit has a parallel interface.

Front of the LCD, this is white characters on a blue background.

Here is the cover removed from the printer, showing the drive belts powering the drive rollers. There is an identical arrangement on the other side of the print engine running the other rollers at the input side of the engine.

Here the back panel has been removed from the entire print engine, complete with the mains input wiring & RFI filtering.
This unit has excellent build quality, just what is to be expected from a £1,200+ piece of industrial equipment.

The bottom of the print engine, with all the main wiring & PCB removed, showing the main drive motors. The left hand geared motor operates the head lift, the centre motor is a stepper, which operates the main transmission for the cards. The right motor drives the ribbon take up spindle through an O-Ring belt.

Card feeder drive motor, this connects to the belt assembly through a timing belt identical to the roller drive system.
All these DC geared motors are 18v DC, of varying torque ratings.

Here is the main power supply, a universal input switch-mode unit, outputting 24v DC at 3.3A.

PSU info. This is obviously an off the shelf unit, manufactured by Hitek. Model number FUEA240.

The PSU has been removed from the back of the print engine, here is shown the remaining mechanical systems of the printer.

A further closeup of the print engine mechanical bay, the main stepper motor is bottom centre, driving the brass flywheel through another timing belt drive. The O-Ring drive on the right is for the ribbon take up reel, with the final motor driving the plastic cam on the left to raise/lower the print head assembly.
The brass disc at the top is connected through a friction clutch to the ribbon supply reel, which provides tension to keep it taut. The slots in the disc are to sense the speed of the ribbon during printing, which allows the printer to tell if there is no ribbon present or if it has broken.

Here is a further closeup, showing the RFID PCB behind the main transmission. This allows the printer to identify the ribbon fitted as a colour or monochrome.
The antenna is under the brass interrupter disc on the left.

The I/O daughterboard connects to the main CPU board & interfaces all the motors & sensors in the printer.

Here is the main CPU board, which contains all the logic & processing power in the printer.

Main CPU. This is a Freescale Semiconductor part, model number MCF5206FT33A, a ColdFire based 32-bit CPU. Also the system ROM & RAM can be seen on the right hand side of this picture.

Bottom of the Ethernet interface card, this clearly has it’s own RAM, ROM & FPGA. This is due to this component being a full Parallel interface print server.

Top of the PCB, showing the main processor of the print server. This has a ferrite sheet glued to the top, for interference protection.

Posted on August 5, 2010 by The Engineer — Leave a comment

HP Photosmart 375

This is a HP PhotoSmart 375 portable photo printer. With built in card reader, screen & PictBridge.
Top of the printer showing the UI Buttons & Screen.

Front of the unit, card reader slots at the top, Pictbridge USB connector at top left. Paper out slot at bottom. Cartridge door is on the right.

Here the cartridge door is open. Takes HP 95 Tri-Colour Inkjet Cartridge.

Battery compartment on the bottom of the unit. A Li-Ion battery pack can be installed here for mobile photo printing.

Specifications label.

Power adaptor & USB connection for PC use.

Rear door opened. Showing the paper feed tray.

Rear door has been removed in this shot. Paper feed roller & platen roller can be seen here.

Paper holder attached to rear door.

Bottom of the top cover, with connections for the buttons & LCD panel.

This is the main PCB of the unit. Controls all aspects of the printer. CPU in center, card reader sockets are along bottom edge. various support circuitry surrounds the CPU.