changeset
[ZPB30A1] new blog about the ZPB30A1
Sat, 16 Apr 2016 19:22:34 +0200
- author
- David Douard <david.douard@logilab.fr>
- date
- Sat, 16 Apr 2016 19:22:34 +0200
- changeset 47
- c2a88ad9de68
- parent 45
- 3eed12f6592b
- child 48
- 0a7b1c6b1796
[ZPB30A1] new blog about the ZPB30A1
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/content/ZPB30A1.rst Sat Apr 16 19:22:34 2016 +0200 @@ -0,0 +1,118 @@ +========================= + ZPB30A1 Electronic Load +========================= + +:Author: David Douard +:Category: Electronics +:Tags: ZPB30A1, electronic load, test equipment + +A few weeks ago, I purchased a cheap electronic load from AliExpress +(`this one`_ to be precise). It's a ZHIYU model ZPB30A1. It's +specifications are: + +- constant current mode +- max voltage: 30V +- discharge current: 0.2A to 9.99A (+/- 0.7% + 1 digit) +- max dissipated power: 60W +- voltage measurement error: 1% + 2 digits + +It supports 2 operation modes: + +- electronic load: in this mode, you can set the current and the + minimum voltage above which it beeps; in this mode, it display the + measured voltage and set current. +- battery capacity test mode: in this mode, you set the discharge + current and the lower voltage limit at which the discharge test + stops. It displays the total discharged capacitu (in Ah) and energy + (in Wh). + +.. image:: {filename}images/ZPB30A1/zpb30a1.jpg + :alt: Overall view of the ZPB30A1 electronic load + +The device looks pretty nice and reasonably well built. It can do 4 +wire measurements. + +The device itself is built around a single ST W60N10 N channel MOS +transistor (100V, 60A, 200W) and a STM8S005K6 microcontroller. + +.. image:: {filename}images/ZPB30A1/zpb30a1_board.jpg + :alt: Main PCB of the ZPB30A1 electronic load + +The shunt resistor is a 10mΩ wire. A very small value that explains +the rather big minimal current of 200mA (which means a voltage drop as +low as 2mV). + +.. image:: {filename}images/ZPB30A1/zpb30a1_mosfet.jpg + :alt: Main transistor of the ZPB30A1 electronic load + +One nice thing with this device is the fact that every component value +is written on the PCB: no need to use the magnifier to read the SMD +parts values. + +The bottom side of the PCB is pretty empty besides the ground plane. + +.. image:: {filename}images/ZPB30A1/zpb30a1_bottom.jpg + :alt: Bottom side of the PCB of the ZPB30A1 electronic load + + +The most annoying thing is the minimum current of 200mA, which pretty +hight. It's obviously not designed for small battery or PSU +testing. + +Another thing is that its limited to CC mode only (does not provide +constant resistance mode nor constant voltage). It's a bit unfortunate +since it's probably only a matter of software. + +Also, the usability is quite rough. For example, to choose the +operating mode (between CC charge and battery capacity test mode), you +have to power off the device and power it on holding the start/stop +button down. + +The last missing feature, for me, is that there is not "output" port +allowing to capture the values when doing a battery discharge +test. The good news is that there is unpopulated port. Looks like some +ISP/serial port directly connected to the microcontroller. Pins are +labelled as G, R, T, L, F and Vc. G stands for ground, and Vc is +obvious. R and T might be Rx and Tx of a serial port. F and L are not +obvious. + +So I've probed a bit to see if there are any signals. + +The overall (messy) setup was: + +.. image:: {filename}images/ZPB30A1/overall_setup.jpg + :alt: Overall testing setup for the ZPB30A1. + +During this test, the electronic load was sunking almost 1A at 30V, +thus dissipating around 30W. The MOSFET transistor was getting a bit +hot. I measured 65°C with my cheap IR thermometer. + +The F pin shows a square signal at 50kHz, and there is some activity on +the T pin. I've used my new Rigol DS1054Z scope to try to find out if +the signal is meaningful. And after playing a bit with the Serial +decoder, I finally found that: + +.. image:: {filename}images/ZPB30A1/DS1Z_serial.png + :alt: Serial signal on the T pin. + +When the ZPB30A1 was actually set up like this: + +.. image:: {filename}images/ZPB30A1/zpb30a1_setup.jpg + :alt: Testing setup for the ZPB30A1. + +So the measured voltage is constantly written on the serial port at +115200 baud, 8N1. The third value is 1 when it is normally operating, +and 0 when the voltage is below the limit. + +However, in battery discharge mode, there is nothing on the serial +line. + +Now, I have to solder a socket in there. Then the next step will be to +see if we can send commands to the ZPB30A1. I may need to learn a bit +about the ST microcontroller... + + + +.. _`this one`: http://fr.aliexpress.com/item/New-Constant-current-electronic-load-9-99A-60W-1-30V-battery-capacity-teste-free-ship/32571919265.html + +
