FZ35 Adjustable Electronic Load Questions - Page 1
Forum section: electronics / testgear

author: PathLoss
author_rank: Contributor
timestamp: September 21, 2019, 05:09:57 am
content: Greetings Everyone,This is my first post here - please go easy on me if I mess up...I have a question about a recently acquired model "XY-FZ35" Electronic Load. I searched the EEVBlog Forum three different ways trying to find a thread on these little loads and came up empty handed. I'm amazed.Here is what one of these loads looks like:This is a small (79x43x56mm) self contained 1.5-25V/5A/35W (max.) adjustable electronic load packaged in the same module type case used for the "Ruideng" power supplies. The load modules have both local control and remote control via a 3.3V TTL RS-232 port.These little loads cost from around $16 USD from IC-Station plus a few bucks for the slow-boat from China, to $23 on Amazon with two-day Prime CONUS shipping.Links:https://www.amazon.com/dp/B07KQS74C6http://www.icstation.com/electronic-load-tester-battery-capacity-adjustable-constant-current-aging-resistor-discharger-voltage-current-power-display-p-13429.htmlSo far this load seems to work OK. I've tested 18650 cells and a USB power bank.Question-1: Can anyone point me to a good thread here on the forum about these loads? Especially about using the serial port?Question-2: Everything over the serial port works for me (via a CH340G USB/UART module)EXCEPTfor the parameter settings. The documentation falls short of providing a working example of the setting commands and I've tried all sorts of combinations. All my attempts so far result in "fail" returning. Has anyone been able to get the setting commands to work over the serial port?I found two videos in English on YouTube by searching FZ35. They're OK but don't cover the serial port.Attached is a copy of the documentation that came with the load. It addresses the serial port on page-2.Thanks for any helpDavid in FloridaAttached: User_Manual_DROK_XY-FZ35_LoRes.pdf 1,035 KB

author: ledtester
author_rank: Super Contributor
timestamp: September 21, 2019, 06:07:11 am
content: I don't have one of these units, but I just wanted to suggest that you might very well get answers directly from DROK or icstation.I found this on DROK's "Contact Us" page:https://www.droking.com/cs/contact-us/and I think icstation is also trying to distinguish itself from the other ebay and aliexpress vendors by providing post-sales support to customer:http://www.icstation.com/contact_us.phpIf you do get an answer please update this thread. It's a neat little device and it's been on my radar for a while.

author: PathLoss
author_rank: Contributor
timestamp: September 21, 2019, 08:31:35 am
content: @ledtester,Thanks for the reply. I did buy my FZ35 from seller DROK on Amazon. I did try to go to their Web site to ask for more information but it wouldn't load for more than a day. But now I see it is loading again, so I'll contact them. The manual link in your post at first-glance seems to be the same printed two-page document scan that came with the device. I attached that scan to my OP. But it's good to have the direct download link; thanks to youI'll try asking for some IC-Station support as well, it's on my list for later today.@ledtester said: "If you do get an answer please update this thread. It's a neat little device and it's been on my radar for a while."I will provide more information as I work with this device (at post time it's only been a few hours of bench time). But I didn't want to start a new thread on this module if there was already a thread on the EEVBlog. I would rather add to an existing thread to avoid fragmentation.I did pull the module apart (no screws involved, two boards coupled by M/F 0.1" headers) and I tried to identify the major components. No surprise on what I found. I'll post anew here with details on what I discovered so far.

author: PathLoss
author_rank: Contributor
timestamp: September 21, 2019, 11:04:45 am
content: * XY-F35 Adjustable-Programmable Major Components. Quick look at the boards and main component part numbers (no part numbers ground off the chips) Links are examples only from the Web, and may not be specific to the device in-built parts. My example is from Amazon Seller DROK. See earlier posts in this thread for links:- TIP122, 100V/5A (8A peak) NPN Darlington, TO-220. This is a gumball part and may be FAKE. But fake or not it is likely OK in this application:https://www.st.com/en/power-transistors/tip122.html- Nuvoton 8051 compatible 8-bit microcontroller, 16MHz (max.), 2.4-5.5VDC, 18KB Flash, 1KB SRAM, 6-ch (max.) PWM, 12-bit 8-ch 500KHz ADC, 2xUART 115,200bps (max.), 1xI2C 400KHz (max.) This may not be exact for this on-board device. There are many variants in this family with subtle production-level P/N differences:Anyone hacked this Nuvoton part? I have not drilled down looking for ISP/JTAG pinouts on the boards yet. Even if they are there this part may be OTP to meet a low price point and prevent Chinese joint-piracy.https://direct.nuvoton.com/en/n76e003at20- Holtek HT1621B 32x24 LCD controller:https://www.holtek.com/productdetail/-/vg/ht1621- XLSEMI XL1509-5.0E1 : 2A 150KHz 40V Buck DC to DC Converterhttp://www.xlsemi.com/[Chinese only it seems].Yeah, I think we know what's going on here. Lack of an English datasheet is probably OK from a high-level view. It's a generic buck that works OK down to the 3.3V main bus from 5V-30V as specified in the FZ35 load specs.https://html.alldatasheet.com/html-pdf/763156/ETC2/XL1509-5.0E1/101/1/XL1509-5.0E1.html- LM324 Quad Op-Amp. This is a venerable part, commonly faked but OK here in terms of functionality. This probably supplies the op-amp in the load loop with the TIP122 pass transistor:http://www.ti.com/product/LM324- Current Sense Shunt Resistor:SMT Pkg Labeled R025, likely 0.025 Ohms.Conclusion:I ask again: Theremustbe a thread about this load module here on EEVBlog. Link anyone? I don't want to fragment previous contributions. I HAVE tried to search for threads about this device - and found nothing. I can't believe I'm starting a seriousNEWthread about this thing here!Have Fun! David in Florida

author: bicycleguy
author_rank: Frequent Contributor
timestamp: September 21, 2019, 06:41:27 pm
content: Quote from: PathLoss on September 21, 2019, 11:04:45 amThe best way to search is almost always google. Type this into location:site:www.eevblog.com/forum/ FZ35Looks like your the man.

author: PathLoss
author_rank: Contributor
timestamp: September 22, 2019, 04:45:12 am
content: Quote from: bicycleguy on September 21, 2019, 06:41:27 pm@bicycleguy,Yup, first I tried here with the Search button on the upper-left of the page, then with the Search box on the upper-right - nothing. Then I went to Google and didsite:www.eevblog.com/forum/ FZ35just like you suggested. Again, nothing. So I guess I am it around here on this topic, for now anyway.Thanks for the suggestion. David

author: dariuskt
author_rank: Newbie
timestamp: September 24, 2019, 06:53:02 pm
content: hi,I have XY-FZ35 and played with it for a while. I also made a simple wrapper for serial communication to easy write some tests and graph them in bash/gnuplot. You might find something useful herehttps://github.com/makerspacelt/fz35-cliIt would help to see what exactly you tried to do so I can just state the mistake if I see it.* Anyways, then sending values you must use NewLine (\n) instead of windows LineFeed and NewLine(\r\n).* Another thing is to pay attention to character count and comma placement. setting amps should be in 1.00A format as 1A or 1.0A won't work.https://github.com/makerspacelt/fz35-cli/blob/master/load.sh#L96* every parameter has its own format for setting it. different number of digits after a comma and so on. e.g.https://github.com/makerspacelt/fz35-cli/blob/master/load.sh#L55btw. my code is written for XY-FZ35 connected via esp8266 with esp-link on it. so it will not work directly with ttyUSB0 device. I did not implement that yet.

author: thm_w
author_rank: Super Contributor
timestamp: September 24, 2019, 11:03:19 pm
content: The TIP122 is less than 20c for a genuine part, so not too expensive.There are two versions:- XY-FZ25 4A 25W$11- XY-FZ35 5A 35W$13Seems like no reason to get the FZ25 for that difference. Good cheap way to measure battery capacity of unusual cells.edit: so much odd test equipment is popping uphttps://www.fasttech.com/products/1023/10037520/9708856-juwei-ud18-5-5mm-dc-usb-3-0-usb-c-lcd-digitalvolt/power USB meter monstrosityhttps://www.fasttech.com/products/1023/10061771/9695167-juntek-dpa-2698-dual-channel-dds-function-signal(100kHz power amp)https://www.aliexpress.com/item/33006560379.html(wireless power supply)

author: PathLoss
author_rank: Contributor
timestamp: September 25, 2019, 03:59:46 am
content: I worked with the XY-FZ35's serial port last night for a couple of hours trying different combinations & permutations of the setup commands. I tried single commands, all commands on a single line, and variations of commands on a single line.No success. In-fact the results were worse than a total failure because sometimes entering a setting command would produce a "fail" output immediately followed with "success" on the next line. But even that weird behavior is not consistent every time. At no time was I able to change any of the settings. I tried the CH340G USB/UART with different USB cables and even plugged it directly into my laptop's USB port, that didn't make any difference. I tried powering the XY-FZ35 from different sources including a 12V battery. That didn't make any difference. The control serial commands always work as expected. Tonight I will fire off emails to China to see if DROK or IC-Station can help with this (I put the emails off until I spent some real time trying to make the setting commands work). Here's where I am right now...* The serial port always works OK for the following control commands:start, Start data outputstop, Stop data outputon, Turn on the load functionoff, Turn off the load functionread, Read product parameter settings* The serial port always FAILS for the following commands:x.xxA, Set load currentLVP:xx.x, Set low voltageOVP:xx.x, Set over voltageOCP:x.xx, Set over currentOPP:xx.xx, Set over powerOAH:x.xxx, Set maximum capacityOHP:xx:xx, Set maximum discharge time* Here are my terminal emulator and USB/UART settings. I am using a CH340G USB/UART module set to 3.3V in Windows 10. The serial connection with the XY-FZ35 load is working OK in both directions:- Set the USB/UART module to 3.3V TTL levels.- Cross TXD and RXD lines.- COM Port: 15 (Yours will Vary)- Baud Rate: 9600 bps- Data bits: 8- Stop bits: 1- Parity bit(s): None- Line Termination: LF (Line Feed). Note; LF, CR, and CR+LF all work.- Hardware Flow control: None- Software Flow control: None- Local Echo: ON+------------+ 3.3V +--------++-------------+ USB | RXD|-->>--<<--|TXD ||PC/Laptop USB|--<<---<<--|USB/UART TXD|-->>--<<--|RXD FZ35|+-------------+ | GND|-->>--<<--|GND |+------------+ TTL +--------+Fig.-1, XY-FZ35 Programmable Load Serial Port Interconnect* I used Termite, a simple RS232 terminal emulator for Windows (link below). I also tried Hyperterminal which works OK when copied over to Windows 10 from a Windows XP machine. Both terminal emulators give me the same result. Here's a link to Termite, it's free. Termite can be installed or run stand-alone:https://www.compuphase.com/software_termite.htm

author: dariuskt
author_rank: Newbie
timestamp: September 26, 2019, 06:00:42 am
content: Looks like there is a pattern. Trie no line ending for commands with numbers at all. That works for me, just tested on my load. That also works on commands without numbers, so looks like I was wrong about \n in my last post.

author: PathLoss
author_rank: Contributor
timestamp: September 26, 2019, 10:28:13 am
content: Quote from: dariuskt on September 26, 2019, 06:00:42 am@dariuskt, You got it! Thank You very much [labai ačiū].So it seems the "control" commands work no matter what the line-end settings are (e.g., CR, LF, CR+LF, NONE, etc.) The "settings" commands will only work if the line-end is set to NONE. But BOTH the "control" commands and the "settings" commands work if the the line-end is set to NONE. Maybe the firmware designer is doing this to add a form of password level access but instead of a password, the access level is determined by the line-end character(s). Hmmm... I've seen this done before in simple industrial PLC's.In the brief time I've been working with the "setting" commands (now that they work thanks to you), I tried sending the setting commands one at a time (works), then I tried sending two or more setting commands comma-delimited with and without a space between them. None of that worked (result is one or more "fail" messages, but sometimes a mix of one or more "fail" results and an occasional "success" result message. In all cases no actual settings were changed.) So it seems each setting command must be sent individually.I will look at the links in your earlier post in this thread. For some reason your earlier post did not appear to me here in the EEVBlog Forum for quite some time. Maybe that's because your post has external links in it which sent it to moderator-inspection before publication. That's OK.I need to "sniff" the actual serial data going to/from the XY-FZ35 module. I would normally do this in Linux as it is easy, but I do not have a working Linux machine handy at the moment (long story); I'm stuck with only a Win10 laptop right now(insert Sad Face). [Or maybe Wireshark in Windows can do serial port sniffing? Dunno.] Since the XY-FZ35 is a 3.3V module on the exposed serial port, maybe I'll try a "Blue/Black Pill" STM32 board or an ESPXXX module as the interloper as they are both native 3.3V GPIO.Again, thanks for your help friend.David in Florida

author: thm_w
author_rank: Super Contributor
timestamp: September 26, 2019, 11:13:47 pm
content: Quote from: PathLoss on September 26, 2019, 10:28:13 amIts easy in windows too, first google result:https://freeserialanalyzer.com/But yes hardware sniffing is always an option.

author: PathLoss
author_rank: Contributor
timestamp: September 27, 2019, 01:50:30 am
content: @thm_w,I appreciate the link - I really do. But...Yeah, I'm skeptical when I see the word "Free" in front of every line on a program's pitch-page, especially if you can't find the real price anywhere on the site. At that point I instinctively know the application is going to be cripple-ware and you are not going to see the price until the very end of the "upgrade" process when they have all your personal and payment information. But I downloaded the program and tried it out in a VM anyway.VirusTotal gave the setup.exe a perfect 0/68 detected (there is no stand-alone version). But it went downhill quickly from there. I got the thing to monitor a serial port, but the likes of Esc[ sequences were missing. The user interface is terrible IMO. Help gives little help. I stayed in crippled mode, fearing to turn on the 14-day full feature "trial". I still have no idea what the uncrippled product costs, I wasn't about do go through that mine-field.TL;DR:Good: 1. VirusTotal 0/68. 2. It will monitor a serial port in most basic way possible while still in free (crippled) mode.Bad: 1. Serious cripple-ware with a 14-day time bomb. 2. No stand-alone version. 3. Really messy UI. 4. Impossible to see the real price until it's (probably) too late. 5. I didn't see ANSI Esc[ sequences, that capability is probably in one of the crippled protocol options. 6. Help isn't very helpful.*A Possible Better Alternative?Take a look at this: "Portmon for Windows v3.03":https://docs.microsoft.com/en-us/sysinternals/downloads/portmonThis is free (for real). It's dated (2012), but it will probably work OK in Win10 (remember: Run as Administrator may be needed). This is one of the old Sysinternals Windows utilities. (Microsoft bought-out Sysinternals some time ago.) Unfortunately, I don't have time to try it out right now.Best Regards, David

author: PathLoss
author_rank: Contributor
timestamp: September 27, 2019, 02:02:02 am
content: IGNORE THIS QUESTION!! I don't know what I was doing here. I was thinking about a voltage source output, the load is the exact opposite. Sorry all... David@dariuskt,I have another question about this XY-FZ35:Does your XY-FZ35 have an output diode to protect it against back-feeding when it is off? If it does have a diode in the output, is the voltage shown on the display measuredafterthe diode (good), orbeforethe diode (bad)? I don't have my XY-FZ35 with me right now. What do you think?Thanks, David

author: dariuskt
author_rank: Newbie
timestamp: September 27, 2019, 05:58:36 am
content: Yes, there is an in-series diode. Also, OVP (Over Voltage Protection) can not be disabled and minimum value possible is 1.5V (they definitely can't load anything lower then diode drop plus drop on the load transistor). The problem with OVP that can not be disabled is that then you hit OVP in normal test conditions the screen starts blinking OVP and you no longer can fix it via UART. Load does not accept any commands. At least I did not find the way without physically pressing the button on the load.

author: tele
author_rank: Newbie
timestamp: November 04, 2019, 11:27:52 am
content: Hi, when using the XY-FZ35 with "Termite" program...you have to go to "settings" and choose at "Transmitted text" > Append nothing.Then you can perform the set commands like OVP:20.0 and so on.

author: meister
author_rank: Newbie
timestamp: December 11, 2019, 02:39:25 am
content: Hi,i wrote a python frontend for the FZ35,Maybe somebody could use it.https://github.com/multigcs/FZ35

author: yellobyte
author_rank: Newbie
timestamp: June 12, 2021, 01:21:04 pm
content: Hi,I have written a control program for XY-FZ25/FZ35 a year ago. Thought I make it public.https://github.com/yellobyte/ElectronicLoad-Control-XY-FZ35Have fun with it!

author: HKJ
author_rank: Super Contributor
timestamp: June 12, 2021, 03:17:09 pm
content: TestController do also support ithttps://lygte-info.dk/project/TestControllerIntro%20UK.html

author: Andre_S
author_rank: Newbie
timestamp: May 27, 2025, 10:47:13 am
content: hi. There is a circuit diagram fz35 ?

author: ledtester
author_rank: Super Contributor
timestamp: May 27, 2025, 12:38:02 pm
content: Quote from: Andre_S on May 27, 2025, 10:47:13 amCheck out this video starting at 23:25:

author: Andre_S
author_rank: Newbie
timestamp: May 28, 2025, 06:59:53 am
content: Thank you.