I decided to take a risk and get one of these RS485 controlled electric loads. Haven't tested so far - waiting for a rs485 dongle .
Spec are supposed to be 500W , 200V , 60A ,CV, CC, CW and CR modes.
While build quality seems OK there is a slight problem that the system uses recycled power Fets . Fets seem original IRFP264 devices rated @ 250V .
(legs are covered with shiny solder to a point , looks crusty close to case ).
The design is very simple - basically a STM32 used to control 8 transistors via op amps.
Read back of voltage and current is done by STM as well. The built in ADC/DAC are 12 bit so appropriate for such design from the 80c .
There is 1 thermal sensors (transistor used as diod ) and room for 2 more sensors that would connect in parallel to the one populated.
Fan is controlled from the ULN2003 - most likely PWN controlled.
I have similar unit. I plan to control it using ESP32, but I didn't come around to it yet. Works nicely using the dongle, though.
I'm attaching a python script if you're interested.. (on second thought, I'm not sure if this is the correct one, but I'll leave it here until proven otherwise)
Script seems to have errors . But thanks anyway.
Tried connecting to the TX and RX port available on the board.
Looks like I am able to get MODBUS RTU data
Well tested the unit from 1.5V to 31V and up to 5A load
the read back was fairly accurate with a slight offset on the current readings of about 10mA .
I was testing the different data groups on Modbus.
The unit uses
Holding Registers for settings
HR2 Enable/ Disable
HR3 Overvoltage (20000 default =200.00V)
HR4 Amp setting in mA
HR9 Over current setting (5500= 55A)
Input registers for readouts
IR6 Voltage Readout
IR7 Current readout
IR8 Power readout
IR9 Resistance setting readout
The fan was not spinning until the unit got hot 45..50C and the speed did change with temperature. So there is some kind of fan control
I lost communication while trying to change register HR5 and was unable to get it back. Hope it comes back to life.
Hi. Are you buy this load from sousim taobao shop? You can found more software for this load on page of this shop. Main io protocol is modbus rtu. You can use any modbus rtu tools .. register definition avaliable ...if you do not have baidu account , please say. I can replace to other cloud.
What is stm32 used on this load ? Thank you
Hi. Are you buy this load from sousim taobao shop? You can found more software for this load on page of this shop. Main io protocol is modbus rtu. You can use any modbus rtu tools .. register definition avaliable ...if you do not have baidu account , please say. I can replace to other cloud.
What is stm32 used on this load ? Thank you
Yes got the load from sousim taobao
I do not have a baidu account so I was not able to get any of the software.
The processor is STM 32F100C8 with 12bit ADC and 12bit DAC . Possible to get more bits out of 12 bit adc via oversampling/averaging. Vendor claims 16 bit resolution.
Dear Sir,
did You bring the load back to life? I faced the same and got lost
.
Hlp pls.
Petr
Hi. Are you buy this load from sousim taobao shop? You can found more software for this load on page of this shop. Main io protocol is modbus rtu. You can use any modbus rtu tools .. register definition avaliable ...if you do not have baidu account , please say. I can replace to other cloud.
What is stm32 used on this load ? Thank you
Software as per attached.
Hi. Are you buy this load from sousim taobao shop? You can found more software for this load on page of this shop. Main io protocol is modbus rtu. You can use any modbus rtu tools .. register definition avaliable ...if you do not have baidu account , please say. I can replace to other cloud.
What is stm32 used on this load ? Thank you
Software as per attached.
Some more software downloaded from the link in taobao. I haven’t test them nor do any virus scan. Use it at your own risk.
I have not tried to get the unit working. Maybe requires a new processor not sure? I have a working unit if someone knows how to extract the firmware I can try.
May be wrong modbus address, see this attachments !
if dc load do not answer from rs-485 you can reset to default uart baud rate.
reset sequience
short 2 pins in CON3 connector see picture
and on picture i mark swd pins fw may be do not locked....
Hi,
I have problem with setting values for measurements. Only first (M1) work correct. If select some other points the I get a message that software not received data from power load after setting value. I tried with few softwares and works same. Don't get any message for other points....
Does anyone had the same problem?
Is the documentation and description of the registers available in English?
Thanks
Hi,
Is the documentation and description of the registers available in English?
Thanks
You can translate 通讯协议.xlsx file from modbus.rar
for test you can use modbuspoll softaware. its work with mbp and mbw files from modbus.rar
I pushed the xls through Google Translate. The translation is a bit rough but it's better than nothing. Attached in case it's of use to anyone.
I pushed the xls through Google Translate. The translation is a bit rough but it's better than nothing. Attached in case it's of use to anyone.
thank you, i have the 150w version of this and at first it worked really well now i dont know why it works,(using modbus poll) but i cant seem to get data back, so for examle i cant see any of 30000 registers, previously i could read for example the measured current and voltage. now they are all zero.
40000 registers work as intended, i can set for example currents in CC mode and the load will pull the specified current from the PSU, but registers on the pc interface will still stay zero no matter what i do .
what could have happened? did i fry the adc on the stm32 ? did anyone had the same problem?