Yes, at some point that idea crossed my mind and I was thinking in using video analytics that "reads" the instruments. But I guess that I'll use different arduino sensors to measure what I need, and use RS-485 to transport the data and avoid the noise that generators can produce.
" ... I have 45 days to modify (or complement) the generators..."
is this to test, prototype, install, test, troubleshoot and get the first one to work, is a partial way ?
or to fully modify 2 different types with new electronics ?
running CAT-6 cables to the units and then to ?? make the units not portable.
also, is this just to monitor ? or to control ?
I can see getting a few values, hour, temperature, volts, HZ, amps, oil pressure, water temperature, RPM.......
how well have you been able to read these values on your test bench ?
RS-485 requires common GND, you will have to take all measurements first.
Hi,
45 to have a functional prototype and then 30 days (business days) to have the final device (I just need 2 for 2 power generators). This devices will install permanently on each power generator, inside a metal case to protect the circuit from external noise, and the communication will be RS-485 (MODBUS) through a shielded wire (less than 1200 mts to the monitoring location). I need only monitoring, no control. My first tests will be this Tuesday and this day I'll take some measurements.
My first approach will be using this sensors:
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Current - HST21 (HST21 -600A)
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Fuel and Water levels: HC-SR04
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Temperature: MAX6675 Maxim/Dallas Semiconductor (Datasheet)
For pilot lights (alerts like oil pressure, water temp, etc.) I'm thinking in capture the signal from the pilot itself and the same for the rotatory switch state (for example like the "Engine Auto Control Selector" - RESET, AUTO, OFF, Manual).
I'm worry about the corrosion that can produce the fuel over the HC-SR04.
For the battery charge (two car 12V batteries) I'm investigating what is the more accurate option.
How often is the water drained off the diesel storage tank? How often and what is the temperature change of the storage tank? Does each generator have it's own diesel fuel tank and what is the shape of the tank? Diesel always has some water in it. It eventually sinks to the bottom of the tank.
I doubt if you have very much success measuring either water or fuel level with a HC-SR04. Lots of people have tried. Echo off the tank sides is the first problem and it changes as the liquid level changes.
Paul
@Paul_KD7HB, there are thoughtful questions and to keep in mind into the measurements. Maybe is better install a 3 -point sensor that sense the liquid at low, medium and high levels?
Radiator water level can be by a float switch.
Most oil tanks have a gauge. Might be easier to monitor the sending unit.
You will be much better of using PZEM-004 AC monitors: they are isolated and measure current, voltage and power plus Hz and Phi on their own. They are natively modbus.
The fuel tank levels should be measured with differential pressure transducers.
Take care of using automotive grade sensorics only.
one of the things that may be desired is Hz of the generated power. not sure how sophisticated this is to be.
Taking a wild guess, the OP will say buying such a module is expensive, but, I have no better way to SAFELY connect mains power for measurement.
as for the fuel tank measurement. not sure how a differential pressure transducer would offer fuel level.
it would seem that most cars use a level sensor, but newer cars monitor emissions leakage by a tank pressure sensor. totally different application than level.
how would you use a DP transducer to monitor fuel tank level ?
I would think that one would have a tank full and tank low sensor. and then calculate run time to guesstimate remaining.
I have no idea how my car knows distance to empty. it get's it wrong, but it still tries.
Thank you very much to all you for your invaluable ideas. I am already researching this options to see which one can best be adapted to my specific needs.
For the fuel level measurement I was found this device that is corrosion resistant and specialized for this purpose:
Fuel Gas Sender Stainless Steel Fuel Sending Unit Marine Boat Water Level Gauge Sensor
And there is a tutorial about its implementation with Arduino:
Measure Fuel Level With Arduino.
let’s assume that the digital unit is RS485 so there is no need for an Arduino.
That leaves us with the Analog panel unit.
The left gauge appears to be oil pressure over water temperature.
The main electrical gauges are [ unknown], HZ and Volts AC
the left most electrical gauge is labeled. 0 to 1.2. I would have guesses AMPS, then then expect reading more in line with 0-120 amps or some such. Volts is labeled 0-300 so we know they can put the 0’s on the readings.
there are some idiot lights on the bottom, low oil pressure, high water temperature, overspeed and over crank.
Not knowing for sure, but the left most selector switch appears to select what is displayed on at least one of the meters.
Phase selector. That would indicate the generator might have a 3-phase output.
That makes sense that you could check volts and amps on each phase
so, the wiring diagram would be needed to explain what the selector switch would be for.
The second selector switch is for ‘engine auto control selector’ settings of off/reset – Auto, Manual, Stop can be selected. Since the OP said this project is observation only, there is no remote control, then that switch may or may not need to be monitored.
There appears to be two switches heat switch and governor motor, but both appear to be optional with caps over the holes.
The last adjustment is a POT with an adjustment for voltage. Assuming this is a large generator and therefor stationary, one might assume that driving a load that is far away, one might want to output 260 volts to get 240 at the load. Or, if the load is close, drop the output to 240.
that leaves the two panel lights on the top, on either side of the gauges and the capped hole for another pressure/sensor gauge.
To boil all that down to an Arduino application.
The two gauges, pressure and temperature may be a Bordon tube for pressure and a thermistor for temperature. That means that neither has an electrical value.
For the 3 electrical meters, all three should permit some form of connection. I would assume test points would be shown on the schematic and possibly accessible under the right cover plate.
What can you do to get some of these readings into an Arduino ?
Block and water temperature should be easy enough. The water temperature will require the addition of an invasive probe to be accurate, or an external problem to Representative in units. The unit would then be calculated to some values.
Volts by a circuit, Hz would be a different circuit. Both of these would be non-invasive, but would require wire connections. Ideally, both would share one set of wires.
Amps by CT, non-invasive, so that one is the easiest of all.
Motor RPM would be able to indicate motor hours. Presence of voltage would be able to indicate generator hours.
Nothing on the panel shows fuel level. So it is assumed there is a large tank, remote, like home heating oil, that has fuel.
The added temperature sensor next to the starting solenoid might be for water temperature as it appear to have an alarm function set for about 225 F/105C
the digital panel is all the same readouts with the addition of a display. hours/battery, etc.
the OP intentionally blocked the panel labels so we cannot try to find schematics.
All that laid out, the project can be clearly laid out as to what reading are IMMEDIATELY required.
That would be phase-1 of the project. Get a fully operational, unit, with outputs of the minimal required values.
Phase-2 would come after troubleshooting failures of Phase-1 and would include the nice-to-have readings.
I would think that part of Phase-1 would be a well documented and with photos, a manual of installation and troubleshooting.
In my view, a local digital display would be required.
Also, since none of this is for control, any processor could be used. Lots of choices there, A MEGA would offer more inputs so that would make your life easier and with the mini-Mega’s the cost is not prohibitive.
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"For the fuel level measurement I was found this device that is corrosion resistant and specialized for this purpose: "
The photos did not show a level sensor or readout. the size of the fuel tank will limit the options.
one of the simpler ways is to put load cells under the tank. costs are way less and the readings can be calculated without too much difficulty. only works for stationary tanks.
@dave-in-nj , sorry for the bad pictures. The "unknown gauge" is "kilo-Amperes" this is a shot with better angle:
All your deductions are correct (I'm not sure about that the digital unit is RS485) .
Sorry if I do not show all the necessary information, but I have only had a first approach to the physical facilities and the owner send me the information by pieces, but this week that begins I'll collect a lot more of data about the generators.
I'll do an inventory about all the readings that are needing and to take into account all the recommendations that you are giving me.
Hz is not a complicated circuit, just fairly CPU intensive. You can use a circuit similar to zero-cross detection circuit. A rectifier-bridge, 2 x 1w 33k resistors ( or 2x (3x 100k parallel) and an opto-coupler. Then you measure the number of times the zero crossing is detected divided by the time divided by 2 is the frequency no ?
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The PZEM-004 AC monitors give Hz, Volt, Amp, Watt, Phi and are galvanically separated.
The modules are not expensive: ~20$ per phase.
Don't ever try to do the details of the AC measurements in the Arduino:
You would need multitasking, since you will have other tasks in //
That will end up in a huge mess, believe me!
Buy a dedicated AC measuring transducer!
Thanks for the advice @RIN67630, I'll do some test with this module.
My guess is amps , volts, hours, temperature, oil pressure, fuel level.
Calculations of litres per hour are easy enough.
I would not offer what is is possible. But rather what can be achieved in a month.
It seems tbe costs for this project will be more than a simple hobby project.
Arduino plus enclosure
Custom circuit board
Fuel sender
(3) voltage sensors
serial output
Connectors screw terminals?
Thermocouple module with board
The ironic part is that the custom circuit board may be the one of the lower cost parts.