I have found the liquid crystal libraries, and a nice Ardino-compatible touch screen, about 350 x 250 in size. It occurs to me that the zero has a data card slot, so I can do most of what I want on the Arduino, without involving a win PC. Probably what I cannot do easily is fancy graphs and printouts.
I can have a start-run switch, and end-run switch, and display maximum power with relevant rpm and torque for the run, fill a predefined table with rpm and kgf figures, with rpm as the "x" axis,
and display table values on screen, maybe with a "scroll" button. I could also write table values to a file with a date and time key. Questions: what are the drivers for the data slot?
Q: do I need to format the data card? Q: can it be written in a windows-compatible format?
Is there a tutorial on this? I will do some searches, and check which version my Zero is.
probably rpm values with 100 rpm as the step, from 0 to 20,000 rpm, makes 200 items.
kgf can be fairly small as torque is 12 N-m max, so about 3.6 kgf max. one decimal would be ok.
low power level would be 5 hp or 3.7 kW at around 7,000 rpm or 5 N-m, 0.5 kgf.
Can I read this on a 70 kg beam, or do I need a 10kg beam? I have a 70kg on order.
Torque is force x distance , so depending upon your arm length to the transducer you can calculate the force . choose a transducer that best fits this - you can do the sums , my guess is 70kg won’t be suitable .
Think about data rates and the amount of data you need to process and store, and what the display needs - see if this will work for what you want to do . You can do some experiments on this before you get into mechanical bits
Hi, @owen-bern
What will the dynamometer be measuring the power of?
Thanks.. Tom.. 
This is for a 50cc watercooled two-stroke, normally rated at 10 hp at 15,000 rpm.
This example will be a bench engine only, based on a copy of a 2005 KTM dirt bike engine.
The aim is to get to 30 hp at 17,800 rpm, but I will try developing the original barrel first.
It is limited by being a single port exhaust, and reed valve intake. First thing is to build the water brake, which has a 100mm diameter rotor, using a "scoop and sling" method. According to calculations, it should be adequate. Testing will show if it works. I am trying to avoid buying huge chunks of aluminium, which tends to cost me 60 to 90 nzd per kg to get to me! considering the commodity price is about $4 nz per kg, this seems excessive.
Several problems:
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I possibly want a Mega 2560 to get enough pins. The screen I an getting is 7 inch, 800x480 pixels, and 16 bit parallel. The base zero I have has no SD drive, and not enough pins.
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Which shields can I use on the Mega? all the SD drives are on MKR boards?
I want to run 2x3-pin instruments, and a 4-pin clock module, that also has an included temperature output. This is 10 + 16 + a few others, for the parallel interface.
Is there another method of jumpering to peripheral boards? -
Are there common pins such as ground and power that I can run more than one peripheral off?
My pin count so far is around 28 on peripherals. -
Also, I need info on any standard connectors and longer distance cables, up to 2 metres.
say 3-wire female-female leads., plus hooking up the double-row female pinblocks on the mega board. I can extend the Dupont 200 mm ones, but it would be nice If I could get longer versions.
What is the limit on crosstalk? Do I need twisted pairs? what is the pairing scheme?
The weight and rpm sensors need to be mounted come way from the board and screen assembly, which needs its own floor pedestal, because of high vibration in the engine test stand. I need to carpenter up a nice test table and monitor/ electronics stand. This will be a step up from modified saw horse mounts I use on propeller engines.
- I also may want control outputs for engine throttle and two sets of ball valve servos in the future.
Some people monitor coolant, air pressure air temperature humidity etc, but that is probably not required running close to standard temperature and pressure. -temp can vary between about 10 degrees C up to 30 degrees C around here.
Would I need to go to a professional grade setup for that, with serial connections to a robotics-type pinout board, and more standard plugs?
I don't want to get into more convoluted PC -resident software at this stage, if I can do most things on an Arduino.
-edit-
I looked at the Zero, and it has over 28 pins. Do I need an MKR zero, or can I add a shield with
an SD drive and still have enough pins?
Will MKR shields go straight on to the Mega, or do I get an accessory drive not on a shield?
I will hold off on buying the mega until I get more info. I can also search for SD drives that are not on shields.
-edit 2-
There is a vast variety of pin counts for external sd drives, also mini and micro.
I have counted 6 pin, 9 pin, 7 pin, 8 pin, double row 10, 12, 14, 16 pin types.
It looks like a mega may be a good bet, but which of these can I use, and what differences?
-probably different "include" modules, more clock cycles? which ones are no good for a mega?
is there a favoured chip ID?
details on some plug-in devices:
1)Screen -16 bit parallel, 3.6v signal lines, TFT SSD1963, 800 x 480 pixels 7 inch.
2)Clock - DS3231, AT24C32 chip. 4 pin.- own battery.
Do I need a special touch screen interface to initialise the clock?
Handy for tagging data, creating filenames.
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Nine-pin micro-sd : 3.3V;GND;DO;CMD;CLK;D3,D2,D1,CD - doesn't look that standard.
no-name - probably should avoid. very little info. -
Duowiesi Mega 2560 R3 + cable- has a good description.
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Celex micro SD 6-pin, SPI interface driven + comes with card for library initialisation??
24mm x 42mm.
5V or 3.3V : GND; VCC(power); MISO,MOSI,SCK(SPI bus);CS(chip select)
Do we need pin number xrefs to get the SD library module and pins to line up? -
Celex SD micro-mini?? pop-up 18.5x17.5mm - 6-pin, same scheme.- probably a micro...
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ShenYang SD 16 pin- J1con 9 or JP1 header 8x2 connections available., 48x31mm., micro
-looks overly complex- -
ShenYang SD 6 pin, various pop-up, micro, and mini formats- similar format to Celex 6 pin.
Query- what libraries do these use? how standard are the pinouts?
Am I better off with mini or micro cards? The minis look more robust for storage and handling.
Are there storage racks and systems available, or should I just copy all the data onto win 11
and one-drive backup? - this is easier to keep track of - then wipe and reuse the cards.
I have bought a mini/micro card reader for the PC, USB connected.
Do the libraries come with pinout diagrams to check that the correct pins are hooked up?
Is there a bus scheme diagram available for common power and ground buses on a prototype board? Are there master power and ground pins that can take the load of all the devices?
Which site section is it in?
Is this the correct forum to be asking all this stuff?
Should I stick to standard shields instead for the SD cards? can the MKR shields be used on the Mega?
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With a 16 bit parallel interface the mega is really the only choice.
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There are hundreds of shields available. far to many to list. typically they will tell what they fit in the ad. I rarely use shields myself preferring to wire in generic modules instead.
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You can hook up as many peripherals to power/ground as you like AS LONG AS you stay under the max current rating of the regulator which I believe is only 200mA's on a mega. For instance sensors and other low power devices are usually ok but things like motors, relays etc. often need a separate power supply. Of the devices you listed the backlight on your chosen display greatly exceeds the capabilities of the onboard regulator. Never forget that Arduino's are microCONTROLLER's not power supplies. Arduino's can control power using transistors and such but they can only supply very low power devices.
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As you know Dupont connectors are standard on Arduino's. which is fine for prototyping. but for permanent use I usually buy Arduino's that do not have the dupont headers soldered on. That way I can solder wires in myself and use whatever connectors I like. As far as wirelength and EMI(crosstalk) that depends on too many factors to give a definitive answer. Twisted and shielded wire always helps but every protocol(I2C, SPI, etc) has different capabilities.
As far as libraries just search Arduino library + the name of your device. The good libraries usually give the requirements in their documentation.
Should I use a wallplug-type 3V power supply, or have a 5v power supply to my prototype board, with dc 5v to 3.3v stepdown? I was planning on using a wall 5v supply through the main usb port
initially.
Wall supply:multi-voltage-dc-universal-power-adapter-3v-4-5v-5v-6v-7-5v-9v-12v, output 30w 2.5 A
Will it run on 3V or does it need 3.3V dc? Do I need two onboard buses with 5v and 3.3V, common ground? If I use a 5V wall adapter, I can jumper back supply and ground to the main Arduino board. Are there pins for this? I see it has a circular plug there as well.
or I can get a 2A 5V wall supply into the Arduino, and a direct jumper out from the Arduino plug to the prototype board. Would this be adequate? does the supply need more regulation?
-edit-
" Sensor Shield for Arduino Mega 2560, with SD Card Recorder (assembled)"
This is from AliExpress.
Will this complicate the attachment of the screen 16 bit parallel interface?
There doesn't seem to be much documentation, but it does seem to have power -in screw terminals. Will I still need to set the screen up on a separate prototype board, and with a separate power supply?
At least, running the SD drive should be more straightforward.
-edit 2-
I see the recommended minimum supply voltage is 6v, but it will run off the 5v through the USB port. Is there sufficient current coming though this 5 V to jump back to the prototype board?
I think I only need a 3.3 step-down at this stage. I have a charger here that runs through the usb.
I will check its maximum output current at 5V.-yes this says 3.0 A at 5V output.
You will need to monitor air temperature, humidity and other correction factors to get accurate results, otherwise you'll never know whether minor changes made a difference for the better or worse.
I am not really looking for minor changes. I think 5 hp gain steps between 10 hp and 30-odd will be fairly clear. 1-2% gains or losses require corrective factors. I think engines are not that consistent on dyno runs, anyway, unless you average over 5 or 6 runs.
at 10 hp, that is a 50% gain, at 25 hp, that is a 20% gain.
Most of the running is to get the pipe tuned into the engine. Speed of sound can vary widely between engines, affecting pipe chamber dimensions drastically.
Most design is done in simulation, and testing verifies that predictions are accurate.
I will do a little research on correction factors and the effect on results. Temperature affects air density, and density may change a fair bit between 17 degrees C and 25 degrees C.
I think I can record ambient conditions by hand, and make a spreadsheet report at a later date.
This can draw nice graphs for me, too.
There is no need to automate to that extent, at this stage.
What I am more interested in is synchronising throttle and two ball valves for water flow before and during each run. I have to idle, then pull up power at, say 7000 rpm, while getting the water brake working, with enough flow to stop it boiling. It only holds half a litre max, and will boil in seconds at full power.
Then it probably needs water level lowered continually throughout the run to keep increasing revs, up to around 19,500 revs maximum.
This is a major handful-managing 3 controls at once!
Maybe I need a feedback monitor of internal brake temperature?
I will look into that.
Also, what is the ball valve relationship of lever angle to flow rate?- likely cosine of lever angle- related, as it shuts off before 90 degrees.
I need to look into fairly torquey servos to move the levers.
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