comparison: content/ZPB30A1.rst
content/ZPB30A1.rst
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| 1 ========================= | |
| 2 ZPB30A1 Electronic Load | |
| 3 ========================= | |
| 4 | |
| 5 :Author: David Douard | |
| 6 :Category: Electronics | |
| 7 :Tags: ZPB30A1, electronic load, test equipment | |
| 8 | |
| 9 A few weeks ago, I purchased a cheap electronic load from AliExpress | |
| 10 (`this one`_ to be precise). It's a ZHIYU model ZPB30A1. It's | |
| 11 specifications are: | |
| 12 | |
| 13 - constant current mode | |
| 14 - max voltage: 30V | |
| 15 - discharge current: 0.2A to 9.99A (+/- 0.7% + 1 digit) | |
| 16 - max dissipated power: 60W | |
| 17 - voltage measurement error: 1% + 2 digits | |
| 18 | |
| 19 It supports 2 operation modes: | |
| 20 | |
| 21 - electronic load: in this mode, you can set the current and the | |
| 22 minimum voltage above which it beeps; in this mode, it display the | |
| 23 measured voltage and set current. | |
| 24 - battery capacity test mode: in this mode, you set the discharge | |
| 25 current and the lower voltage limit at which the discharge test | |
| 26 stops. It displays the total discharged capacitu (in Ah) and energy | |
| 27 (in Wh). | |
| 28 | |
| 29 .. image:: {filename}images/ZPB30A1/zpb30a1.jpg | |
| 30 :alt: Overall view of the ZPB30A1 electronic load | |
| 31 | |
| 32 The device looks pretty nice and reasonably well built. It can do 4 | |
| 33 wire measurements. | |
| 34 | |
| 35 The device itself is built around a single ST W60N10 N channel MOS | |
| 36 transistor (100V, 60A, 200W) and a STM8S005K6 microcontroller. | |
| 37 | |
| 38 .. image:: {filename}images/ZPB30A1/zpb30a1_board.jpg | |
| 39 :alt: Main PCB of the ZPB30A1 electronic load | |
| 40 | |
| 41 The shunt resistor is a 10mΩ wire. A very small value that explains | |
| 42 the rather big minimal current of 200mA (which means a voltage drop as | |
| 43 low as 2mV). | |
| 44 | |
| 45 .. image:: {filename}images/ZPB30A1/zpb30a1_mosfet.jpg | |
| 46 :alt: Main transistor of the ZPB30A1 electronic load | |
| 47 | |
| 48 One nice thing with this device is the fact that every component value | |
| 49 is written on the PCB: no need to use the magnifier to read the SMD | |
| 50 parts values. | |
| 51 | |
| 52 The bottom side of the PCB is pretty empty besides the ground plane. | |
| 53 | |
| 54 .. image:: {filename}images/ZPB30A1/zpb30a1_bottom.jpg | |
| 55 :alt: Bottom side of the PCB of the ZPB30A1 electronic load | |
| 56 | |
| 57 | |
| 58 The most annoying thing is the minimum current of 200mA, which pretty | |
| 59 hight. It's obviously not designed for small battery or PSU | |
| 60 testing. | |
| 61 | |
| 62 Another thing is that its limited to CC mode only (does not provide | |
| 63 constant resistance mode nor constant voltage). It's a bit unfortunate | |
| 64 since it's probably only a matter of software. | |
| 65 | |
| 66 Also, the usability is quite rough. For example, to choose the | |
| 67 operating mode (between CC charge and battery capacity test mode), you | |
| 68 have to power off the device and power it on holding the start/stop | |
| 69 button down. | |
| 70 | |
| 71 The last missing feature, for me, is that there is not "output" port | |
| 72 allowing to capture the values when doing a battery discharge | |
| 73 test. The good news is that there is unpopulated port. Looks like some | |
| 74 ISP/serial port directly connected to the microcontroller. Pins are | |
| 75 labelled as G, R, T, L, F and Vc. G stands for ground, and Vc is | |
| 76 obvious. R and T might be Rx and Tx of a serial port. F and L are not | |
| 77 obvious. | |
| 78 | |
| 79 So I've probed a bit to see if there are any signals. | |
| 80 | |
| 81 The overall (messy) setup was: | |
| 82 | |
| 83 .. image:: {filename}images/ZPB30A1/overall_setup.jpg | |
| 84 :alt: Overall testing setup for the ZPB30A1. | |
| 85 | |
| 86 During this test, the electronic load was sunking almost 1A at 30V, | |
| 87 thus dissipating around 30W. The MOSFET transistor was getting a bit | |
| 88 hot. I measured 65°C with my cheap IR thermometer. | |
| 89 | |
| 90 The F pin shows a square signal at 50kHz, and there is some activity on | |
| 91 the T pin. I've used my new Rigol DS1054Z scope to try to find out if | |
| 92 the signal is meaningful. And after playing a bit with the Serial | |
| 93 decoder, I finally found that: | |
| 94 | |
| 95 .. image:: {filename}images/ZPB30A1/DS1Z_serial.png | |
| 96 :alt: Serial signal on the T pin. | |
| 97 | |
| 98 When the ZPB30A1 was actually set up like this: | |
| 99 | |
| 100 .. image:: {filename}images/ZPB30A1/zpb30a1_setup.jpg | |
| 101 :alt: Testing setup for the ZPB30A1. | |
| 102 | |
| 103 So the measured voltage is constantly written on the serial port at | |
| 104 115200 baud, 8N1. The third value is 1 when it is normally operating, | |
| 105 and 0 when the voltage is below the limit. | |
| 106 | |
| 107 However, in battery discharge mode, there is nothing on the serial | |
| 108 line. | |
| 109 | |
| 110 Now, I have to solder a socket in there. Then the next step will be to | |
| 111 see if we can send commands to the ZPB30A1. I may need to learn a bit | |
| 112 about the ST microcontroller... | |
| 113 | |
| 114 | |
| 115 | |
| 116 .. _`this one`: http://fr.aliexpress.com/item/New-Constant-current-electronic-load-9-99A-60W-1-30V-battery-capacity-teste-free-ship/32571919265.html | |
| 117 | |
| 118 |
