Rough description of the scope:
Hardware: An electronic circuit that is capable of driving a current output (4-20 mA nominal, current limits 3.4 to 22 mA) into a load of maximum 900 ohms.
Powered by a USB charger or battery. This means the circuit will have to convert the supply voltage level to a nominal 24 V or higher in order to be able to deliver the maximum current at maximum load.
- one Amphenol 1 Port Female Type B USB Connector for the USB power,
- one M12 Panel Mount Connector, 4 Pole Socket for the current output,
- optional: one communications interface, USB (it is also acceptable to use a Bluetooth interface)
LED's indicate power (green) and output active (red).
The circuit is housed in a robust enclosure, metallic or plastic with all electrical connections and LED's on the same face.
The default output current upon switching on of the electronics is 0 mA.
Software: The software is split in two parts:
- Software in the electronics that drives the current output, and
- Software that runs on an Android tablet or Windows laptop which acts as the HMI.
The software in the electronics receives values from a .txt or .csv file that contains positive, fixed point integers between 0.000 and 1.000. This file may contain many thousands of values, representing a long time series.
A special character will trigger the software to start reading at the first value again, thus creating a circular file that never ends.
Each consecutive number read from the file is scaled in the HMI software to an adjustable zero and span (nominal 4-20 mA). This adjustment is also required to allow compensation for any DA conversion inaccuracies and to move beyond the nominal range of 4 to 20 mA.
The output current update time is adjustable in the HMI software from a minimum of 50 msec to 1 second (50, 100, 200, 500, 1000 msec).
The software in the HMI allows:
- Importing/selecting a .txt/.csv file from a 'library folder' on the tablet or laptop that contains the output values. These types of files can created in Excel for instance, that is not in the scope.
- A 'button' to start and stop reading values from the file and outputting them as current.
- Scaling of the values in the .txt/.csv file to the mA output (default is 0.000 to 4 mA and 1.000 to 20 mA).
- Directly selecting an output value, independent of a .txt/.csv file. Selection of an output value either by typing in a numeric value between 0 and 100 % or by selecting one of eleven 'buttons' with fixed values 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 %.
- Setting of the cycle time for the update time of the current output when reading from the .txt/.csv file.
- Showing the numeric value and a trendline of the set value of the current output. The time (X) axis of the trend is scaled automatically to show at least the last 100 values when reading from the .txt/.csv file. In manual mode it shows the last 100 seconds. The value (Y) axis of the trend is scaled 0 to 100 %.
A real-time clock is not required in the electronics, only an internal clock to time the update cycles.
A separate mA indicator will be added in the output circuit. That is not included in the scope.
This project is based on building a single working prototype.
More specific information is available upon request.
17 pekerja bebas membida secara purata €527 untuk pekerjaan ini
Hi there, I am interested in your project because I have done some analogue converter circuits for my company. To me the challenging part will be making interfacing software and the trending part.
I did my masters in electronics engineering. I have experience in designing various kinds of circuits. I did a number of works with arduino. I will be glad to help you in this work.
I am already working on a similar project for a client. This job will be an upgrade to that. We promise a robust, versatile, microprocessor controlled unit bases on standard components, especially the power modules.