ea-ps_2084-03b
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ea-ps_2084-03b [2015/05/26 18:06] – add documents kingkevin | ea-ps_2084-03b [2015/05/27 22:21] – [connection] kingkevin | ||
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+ | |||
+ | ====== 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 [[# | ||
+ | |||
+ | ===== 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://uni-trend.com/ | ||
+ | |||
+ | ==== connection ==== | ||
+ | |||
+ | 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. | ||
+ | |||
+ | 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. | ||
+ | |||
+ | More details about the cable and modification is described in this picture: | ||
+ | |||
+ | 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. |
ea-ps_2084-03b.txt · Last modified: 2024/01/07 17:49 by 127.0.0.1