ea-ps_2084-03b
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ea-ps_2084-03b [2015/05/26 18:06] – add documents kingkevin | ea-ps_2084-03b [2022/02/10 11:56] – update git links kingkevin | ||
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* set voltage and current: in 0.1 V and 0.01 A steps | * set voltage and current: in 0.1 V and 0.01 A steps | ||
* wide voltage range (0-50 V): 0-84 V, 0-3 A (not a lot, but enough for electronics), | * wide voltage range (0-50 V): 0-84 V, 0-3 A (not a lot, but enough for electronics), | ||
- | * silent: | + | * silent: |
* have an earth connection: on the front panel | * have an earth connection: on the front panel | ||
* not expensive: ~ 80 € | * not expensive: ~ 80 € | ||
* not noname: Elektro-Automatik (never heard of it, but it's German and they have a decent website) | * not noname: Elektro-Automatik (never heard of it, but it's German and they have a decent website) | ||
* provide a communication interface: USB with proprietary documented protocol | * provide a communication interface: USB with proprietary documented protocol | ||
+ | |||
+ | {{: | ||
Here some more documents about this power supply: | Here some more documents about this power supply: | ||
Line 33: | Line 35: | ||
* [[http:// | * [[http:// | ||
* [[http:// | * [[http:// | ||
- | * [[http:// | + | * [[http:// |
+ | |||
+ | ====== measurement ====== | ||
+ | |||
+ | When powering the device on, I noticed that the voltage on the display did not change while I was turning on the knob. | ||
+ | But the Digital Multi-Meter (DMM) actually shows that the voltage actually does change. | ||
+ | Just the reading on the screen is inaccurate. | ||
+ | |||
+ | It was time to measure how inaccurate this power supply is. | ||
+ | But doing that manually just takes to long. | ||
+ | So I decided to implement the protocol to control the the power supply, and I will measure the set output using a DMM connected to the computer. | ||
+ | |||
+ | {{: | ||
+ | |||
+ | ===== power supply ===== | ||
+ | |||
+ | To control the power supply I implemented the protocol described in the {{: | ||
+ | The source code is available on [[https:// | ||
+ | |||
+ | The [[https:// | ||
+ | It will set the voltage and current which are set, actual (measured by the power supply), and [[# | ||
+ | |||
+ | Using [[https:// | ||
+ | These probably allow you to flash the firmware or calibrate the power supply. | ||
+ | ===== multimeter ===== | ||
+ | |||
+ | To measure the output of the power supply I used two [[http:// | ||
+ | These are good multimeters for electronics which you can get [[http:// | ||
+ | More functions and its accuracy are available in the [[http:// | ||
+ | |||
+ | ==== connection ==== | ||
+ | |||
+ | === UT-D02 === | ||
+ | |||
+ | The DMM comes with an RS232 [[http:// | ||
+ | To connect to the PC you need a RS232 to USB converter (are PCs with COM ports still manufactured? | ||
+ | |||
+ | The cheapest RS232 to USB converter one is based on the CH341 chip. | ||
+ | Sadly the 7O1 mode used by the multimeter [[http:// | ||
+ | I also tried the [[https:// | ||
+ | |||
+ | I also has an old ARL3116 based RS232 to USB converter, but there too the mode didn't seem to be supported. | ||
+ | |||
+ | Finally I found a FT232-based RS232 to USB converter. | ||
+ | This is an expensive cable (but good quality), from an evil company, and it worked. | ||
+ | |||
+ | Here is the schematic of this cable: | ||
+ | |||
+ | {{: | ||
+ | |||
+ | But instead of using it, I decided to connect the cable to a CP2102-based UART to USB converter. | ||
+ | Then you have to keep two things in mind: | ||
+ | * RS232 signals are between -12 to +12 V, while UART uses 0-5 V. This was solved by simply using the 5 V pin from the converter to power the cable. | ||
+ | * RS232 signals are inverted compared to UART. This was solved by inverting the signal using an NPN transistor and two resistors. | ||
+ | |||
+ | ^ UT-D02 wire ^ CP2102 UART signal ^ PNP ^ | ||
+ | | green | GND | | | ||
+ | | yellow | GND | | | ||
+ | | orange | 5V | | | ||
+ | | | GND | E | | ||
+ | | | 5V + 10kΩ | C | | ||
+ | | brown + 10kΩ | | B | | ||
+ | | | RX | C | | ||
+ | |||
+ | {{: | ||
+ | |||
+ | === UT-D04 === | ||
+ | |||
+ | For the second multimeter I used a [[http:// | ||
+ | This time the data doesn' | ||
+ | |||
+ | ==== communication ==== | ||
+ | |||
+ | To read the data from both multimeter I used [[http:// | ||
+ | It supports the [[http:// | ||
+ | |||
+ | Once [[http:// | ||
+ | < | ||
+ | sigrok-cli --driver uni-t-ut61e-ser: | ||
+ | </ | ||
+ | or | ||
+ | < | ||
+ | sigrok-cli --driver uni-t-ut61e: | ||
+ | </ | ||
+ | depending on the cable. | ||
+ | |||
+ | ====== experiments and results ====== | ||
+ | |||
+ | I've run 5 experiments: | ||
+ | * go from 0 V to 84 V in 0.1 V increments, without any load | ||
+ | * go from 0 V to 84 V at 1.0 A in 0.1 V increments, with a 678 Ω load | ||
+ | * go from 0 V to 11 V at 1.0 A in 0.1 V increments, with a 10.2 Ω load | ||
+ | * go from 0 A to 3 A in 0.1 A increments, with a short | ||
+ | * go from 0 A to 1 A at 10 V in 0.01 A increments, with a 10.2 Ω load | ||
+ | |||
+ | After changing a value I've waited 3 seconds for the measurements to stabilized. | ||
+ | |||
+ | The measurements and accuracy calculations are available in this {{: | ||
+ | |||
+ | Here are the resulting graphs: | ||
+ | * go from 0 V to 84 V in 0.1 V increments, without any load | ||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | * go from 0 V to 84 V at 1.0 A in 0.1 V increments, with a 678 Ω load | ||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | * go from 0 V to 11 V at 1.0 A in 0.1 V increments, with a 10.2 Ω load | ||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | * go from 0 A to 3 A in 0.1 A increments, with a short | ||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | * go from 0 A to 1 A at 10 V in 0.01 A increments, with a 10.2 Ω load | ||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | |||
+ | As you can see the measured values are most of the time higher than the set values, but within the 0.2 % accuracy (to 84V or 3A). | ||
+ | But the actual values displayed by the power supply is way below what is set, and outside of the accuracy, particularly on the low voltages. | ||
+ | |||
+ | Conclusion: don't trust the displayed voltage (it's too low), but you can be confident the output is right (except for the very low voltages and currents). | ||
+ | |||
+ | ====== teardown ====== | ||
+ | |||
+ | Well laid out, good components, german quality ;) | ||
+ | |||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | |||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | |||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | {{: | ||
+ | |||
+ | ====== conclusion ====== | ||
+ | |||
+ | pro: | ||
+ | * fulfils all initial power supply criteria | ||
+ | * **set output is within accuracy** | ||
+ | * good design, lay out, quality components | ||
+ | * fast first contact response | ||
+ | |||
+ | contra: | ||
+ | * output is not switched of completely | ||
+ | * **measured value is up to 0.4 V lower than output voltage** | ||
+ | * second digit after . of voltage is always 0 and not settable (it should not be displayed in this case) | ||
+ | * second digit after . of voltage is always 0 and does not show measured value (the actual measured data is precise enough to show this digit) | ||
+ | * can skip fast knob turns | ||
+ | * USB cable does no fit in port because of the indent | ||
+ | * information in english programming manual missing | ||
+ | * small mistakes in programming manual | ||
+ | * can not be calibrated by end user, and vendor only calibrates if under warranty | ||
+ | * no contact support |
ea-ps_2084-03b.txt · Last modified: 2024/01/07 17:49 by 127.0.0.1