Affordable Power Supply with Ethernet/LXI? - Page 1
Forum section: electronics / testgear

author: nightfire
author_rank: Frequent Contributor
timestamp: March 12, 2024, 10:53:20 pm
content: SItuation: I like to have a classic adjustable power supply with several twisting knobs for interactive fiddling around, but for some scenarios I would like to be able to adjust and get values from several devices at once, like power supply, electronic load, multimeter(s).So I thought about automating stuff with scripts (SCPI/LXI) and connect everything in the future via ethernet, as this is simpler than fiddling around with multiport serial boards or multiple USB->serial (DB9) converters, especially when you have devices that use a special pinout.One usage scenario that I envision would be the charging of batteries (photographic stuff, like camera batteries etc.) and controlled discharging to measure capacity and discharge curve.Or powering some USB-based charging stuff and measuring things like throughput to verify what embedded logic or the 20€ USB-gizmos (USB wattmeters) tell me.Question here: Which brand or model of power supply would be affordable, reliable and is manageable via Ethernet and Open-Source Software (resp. some other freely available software like testcontroller or Sigrok) where I can put my stuff in and maybe do a little scripting from my PC?The Power Supply would have to be able to do 15V with 2A.Or are there affordable solutions to retrofit some LXI->serial converters to existing gear like a Fluke 45 or a GW Instek PSP405?

author: abeyer
author_rank: Frequent Contributor
timestamp: March 13, 2024, 01:54:16 am
content: Quote from: nightfire on March 12, 2024, 10:53:20 pmThe siglent spd1000s are <$300 new. I don't much care for the front panel controls but if the goal is ethernet remote, that doesn't matter.If you're looking cheaper than that, maybe shop around for deals on a used HP bench supply and used/NOS ethernet-gpib interface. That might be the best price/reliability balance, though you're notthatfar behind just buying the new Siglent w/ ethernet built-in.

author: tautech
author_rank: Super Contributor
timestamp: March 13, 2024, 02:03:41 am
content: Quote from: abeyer on March 13, 2024, 01:54:16 amWell under @ 229 Euro for the 16V 8A version.https://www.siglenteu.com/power-supplies/spd1000x-series-programmable-dc-power-supply/Extremely low noise and with sense terminals.Supports Easypower, SCPI, LabView driver remote control.https://www.siglenteu.com/service-and-support/firmware-software/dc-power-supplies< scroll down to SDP1000X.

author: BennoG
author_rank: Frequent Contributor
timestamp: March 13, 2024, 09:06:22 pm
content: is e-bay an option, if you are patient you can get a decent psu with LXI for les than $200.I have my eye on one at the moment. 60V 12ABenno

author: nightfire
author_rank: Frequent Contributor
timestamp: March 13, 2024, 09:32:53 pm
content: Thanks @all for confirming my thoughts so far, that it could whether be the Siglent 1168X or some used big brand like HP.@tautech: Unfortunately we have 19% sales tax in germany, so thats on top of t he 229€ siglenteu quotes.... :-(

author: thm_w
author_rank: Super Contributor
timestamp: March 13, 2024, 09:51:18 pm
content: So your budget is what?

author: alm
author_rank: Super Contributor
timestamp: March 14, 2024, 12:01:14 am
content: Quote from: nightfire on March 12, 2024, 10:53:20 pmNot sure about LXI to serial, but VXI-11 (which is one of the protocols that makes up the LXI standard) to GPIB is common. There are some commercial devices from HP, Tektronix etc that occasionally come up on eBay, and there are DIY solutions likeYaugiorThis Raspberry Pi based solution. If you have other devices with GPIB you would like to control, then a VXI-11 to GPIB adapter that can address multiple instruments (the commercial ones can do it, not sure about the Yaugi) and a systems power supply with GPIB from brands like HP, Philips, etc may well be the cheapest solution.Used systems power supplies with GPIB sometimes go for less than the costs of shipping if you can deal with the size. They are more optimized for remote control than bench supplies with a remote control port slapped on. Things like much faster down programming due to an active device pulling the output down instead of waiting for the output caps to be passively discharged through the load (response time from max voltage down to 0V with no load might be in seconds). Siglent not even mentioning programming response times in the SPD1000X datasheet does not make me hopeful about the performance. Clearly this remote operation performance is not a priority for those power supplies.

author: tautech
author_rank: Super Contributor
timestamp: March 14, 2024, 12:36:40 am
content: Quote from: alm on March 14, 2024, 12:01:14 amSo why would there be a list of App notes on remote control usage ?https://siglentna.com/application-notes/spd1000x-series/

author: thm_w
author_rank: Super Contributor
timestamp: March 14, 2024, 12:54:31 am
content: Almost any modern LXI PSU should have a constant current load or some fixed resistance on the output, its going to be fast enough to discharge the caps inside within a matter of 100-500ms. I'm sure the Siglent is capable of that, maybe someone can measure it. Sure its not lightning fast but its fine for what is described here.There may be some PSU's with significant load capability that could test a battery on their own (Keithley 2306, 2308, ~3A) but they are not LXI, and usually not that cheap.

author: 44kgk1lkf6u
author_rank: Regular Contributor
timestamp: March 14, 2024, 04:22:45 am
content: I have written programs for both Siglent and HP power supplies. And if I had to get one for my home, I would likely get an used HP and make use of my Xyphro GPIB to USB adapter.Here's my fuss. The Siglent power supplies do not support triggering a measurement from SCPI. Current and voltage are measured once every 500 ms. You can not synchronize it to anything. The measure command returns the value from the previous measurement, but the time since the previous measurement can be anywhere from 500 ms to 0 ms. It makes it hard to do things like incorporating the power supply as part of a feedback loop or measuring the current consumption of a device over time. I had to do the latter this week at work where I had access to both a Siglent SPD3303X and an HP 6612C. I ended up using the HP 6612C via its HP-IB port. Siglent also has some firmware bugs such as allowing the output to be set to NaN or not allowing a space after a comma in the SCPI command. The ones with graphical displays do not allow zooming in on the current and voltage versus time plot. While we're on it, their banana plugs also have a spacing that is not ¾ in.By the way, you should probably get a GPIB adapter anyway if you plan to get more equipment to connect to the network and you want to save money. It allows you to buy used things. I use the open-source Xyphro GPIB to USB adapter because it works with Linux out of the box unlike the HP and NI ones. I don't know about Ethernet.

author: tautech
author_rank: Super Contributor
timestamp: March 14, 2024, 05:45:12 am
content: Quote from: 44kgk1lkf6u on March 14, 2024, 04:22:45 amCorrect, instead 20mm however that does not apply to the SPD1000X series which do have 3/4" terminal spacings.

author: Berni
author_rank: Super Contributor
timestamp: March 14, 2024, 06:35:55 am
content: The Rigol DP832 is also a good programmable lab PSU, costs a bit more but has 3 independent channels.Tho aiming for all 100% Ethernet for your SCPI automation needs is probably not the best idea, since many instruments don't have ethernet (it is more common on modern gear, but still not ubiquitous) and brindging LAN onto instruments with RS232 or USB is not that simple, probably easiest is with a RaspberryPi.USB is a lot easier to convert just about anything into, so you can have all of your bench going into a big USB hub and then you can have a simple single cable going to your PC.I do have a Agilent GPIB to LAN bridge in my equipment rack to help connect the heavy ancient boatanchors from the 80s and 90s. Since all of them are so old they only speak GPIB. But since you can daisy chain GPIB, it made the GPIB to LAN bridge a convenient solution.

author: alm
author_rank: Super Contributor
timestamp: March 14, 2024, 08:19:47 pm
content: Quote from: tautech on March 14, 2024, 12:36:40 amBecause their sales people want to sell the power supplies for remote control, but the engineers are not willing to guarantee any specifications regarding remote control? Would you use an op-amp without an offset voltage specification for an application where offset voltage is important? Any feature that does not have guaranteed or typical specifications is clearly not a priority for the manufacturer. More like a "sure, we can add a LAN port for $5" that came late in the product design cycle.

author: nightfire
author_rank: Frequent Contributor
timestamp: March 14, 2024, 09:27:08 pm
content: Wow, thanks again for the input and the insights in the inner working of a Power Supply regarding update cycles etc.!To get a better grasp of the situation: The stuff is for my little home lab, where I also will use it to explore things- so usage for partly educational purpose ;-)And, as my existing equipment is not bad, it is whether not connectable at all (some small <100€ Power supplies, some of the linear and old), Multimeters (my bench DMMs are more than 20 years old), and some new stuff that has Ethernet.Those Ethernet-capable devices are a Korad electronic load and some entry level Rigol scope. So for me the though was, that I could look while expanding my gear for remote control for recurring tasks I would perform, where repeatability makes sense or is crucial to the task.As for connectivity, Ethernet for me is easier to maintain than a load of USB devices, and in my experience less prone to error that USB->Serial connections, at least at the level of swtiching/cabling involved. Not speaking tho for the inner goods or implementation in the device(s) themselves.In my last job I was also responsible for administering the OOBMS platform in a datacenter, mainly consisting of cyclades TS3000 console servers, and some power monitoring devices where we used Modbus over RS485 and over serial converters to Ethernet (to the main Server)- so I eperienced some share of stuff that can happen in this field.Anyway ,for the upcoming projects even a mediocre response time or readout behaviour of the mentioned Siglent PS are ok enough for the task- when I do some comparison and tests of charging/discharging camera batteries and similar stuff, I am talking about changing parameters and getting them every 1s or 5s, so no need for immediate response. Also some measurements via other multimeters would be taken somewhere, that would be deemed authoritative for the task at hand, so I do not need to rely on precision measurements from the PS itself.Interesting idea to get some USB->GPIB converter, or Ethernet ->GPIB.I admit the the open source Xyphro GPIB to USB looks nice, so I would really like to get some hands-on experience- Penguin compatibility is nice, because there is another factor that I took into account whilst planning purchases: I will as one of the upcoming projects rig up an old PC I assembled for cheap from really solid parts as a Unix-based Workstation under FreeBSD and also do some measurement work here.So Ethernet/LXI could be the protol that will involve the least number of drivers and proprietary windows programs to get some communication done.Ethernet->LXI converters are a cool idea, I would like to hear how well they perform under non-Windows environments.

author: Berni
author_rank: Super Contributor
timestamp: March 15, 2024, 07:30:58 am
content: The reason you had constant issues with Modbus and RS485 is that they are shitty protocols that are often implemented in a way that is not robust enough for the environment they end up used in.You should not need any special drivers to do things over USB. All properly made test equipment should be using the same USBTMC driver. Any PC side VISA implementation you use will automatically detect and identify the instrument as soon as you plug it in. If it does not simply work out of the box like that then the manufacturer of your test gear has fucked up.That being said RS232 is indeed not plug and play like that. You do need to specifically tell the VISA software to treat a certain COM port as a instrument, but once you do that you are set forever. When you unplug and replug it it will always pick it up (Unless you are using shitty chinese USB to RS232 dongles that don't have serial numbers, throw those in the trash please). Some cheep instruments that have USB actually have a USB to RS232 chip inside, so those are configured the same way.Also there is nothing wrong with having a mix of Ethernet, USB, GPIB, PXI..etc test gear connected to a computer. They all show up in the VISA software exactly the same once detected, communication to all of them is done trough the exact same call to the VISA dll function. So your test automation script does not even know over what physical protocol it is talking to the instrument, it is the job of the VISA library to take care of that nitty gritty.Also don't just blindly go for the 'standard' National Instruments VISA software, it is one of the worst bare bones implementations. I personally recommend using Keysight IO VISA as it has lots of nice features and it is also free. (Rigol also has its own VISA called UltraSigma or something, i am not that much of a fan of it) And don't worry it is not Keysight instruments only. It will talk to any IVI or PXI compliant instrument, or even talk to your own DIY made test equipment as long as you follow the standards.

author: nctnico
author_rank: Super Contributor
timestamp: March 15, 2024, 08:08:01 am
content: Then again, if you use ethernet exclusively (either direct or through a ethernet-GPIB adapter), you can skip dealing with Visa and use a simple library which talks to devices directly over the network. Like Pyvisa for Python or just open a socket and start sending / receiving text for simple control applications. Personally I never had much luck using VISA from any vendor. Mostly resulted in getting the wrong version for the software to be used, missing DLLs or unsupported OS. I don't want to deal with that kind of crap. KISS is king.

author: Berni
author_rank: Super Contributor
timestamp: March 15, 2024, 08:53:23 am
content: PyVISA still handles all of those. It can access all the usual interface types of USB,LAN,RS232..etc be it using official VISA DLLs or using the pure python re implementation of VISA that needs no DLL.Id imagine getting any of those official VISA library implementations on Linux is a huge pain. But for Win 7 and Win 10 i never had any issues with the official VISA. Run the installer, next, next next, open it up to detect instruments and grab the address, run the testing script and it works.If anything i had issues with bad implementations on the instrument side for some cheep Chinese or badly designed test gear where the remote control misses commands or locks up or starts giving garbage etc.. High quality brand name test gear never had those issues.

author: BennoG
author_rank: Frequent Contributor
timestamp: March 15, 2024, 09:24:33 am
content: Have you seen the load of shit NI-VISA installs on your system. (yes NI-VISA) is needed to run PyVISA.Benno

author: alm
author_rank: Super Contributor
timestamp: March 15, 2024, 10:02:04 am
content: You can use PyVISA with PyVISA-py on any platform which will support a bunch of protocols like VXI-11, USBTMC, plain TCP, serial and on Linux most GPIB interfaces. I've read R&S VISA is also pretty light weight.

author: Berni
author_rank: Super Contributor
timestamp: March 15, 2024, 10:32:47 am
content: Quote from: BennoG on March 15, 2024, 09:24:33 amHence why i advise against using the National Instruments VISA implementation in my post above. (As a lot of people think they need it)It is not strictly required to have their implementation. You can install any other vendors VISA implementation (Keysight,Rigol, R&S...etc) and it places in a API compatible visa.dll that other applications will happily use it. Any implementation can be used in its place as long as it follows the VISA spec from the IVI Foundation.

author: nctnico
author_rank: Super Contributor
timestamp: March 15, 2024, 04:47:09 pm
content: Quote from: BennoG on March 15, 2024, 09:24:33 amNever. As Alm noted, there is a python library (PyVISA-py) which takes care of instrument communication. So far this has worked very well for me on various instruments (direct LAN or through a Prologix ethernet to GPIB adapter).

author: djacobow
author_rank: Super Contributor
timestamp: March 15, 2024, 05:13:28 pm
content: Quote from: nctnico on March 15, 2024, 04:47:09 pmThat's right, I believe PyVISAcanuse the NI libraruy, but there is an all-python implementation and that's what I use 100% of the time. I use PyVISA to control a lot of instruments with no problems at all:Rigol DS1104Z (ethernet)Rigol DS2072 (ethernet)Rigol DG1022 (usb)Rigol DM3068 (usb) *Rigol DP832 (usb) *Korad KA3005 (usb serial)Siglent SDM3055 (usb serial)Instek GPP4323 (ethernet) *Maynuo DC load (serial via adapter)The ones with asterisks are used in an automated production environment.That said, for something serial or serial over usb I sometimes find it more convenient to just send and receive commands directly without PyVISA; I don't think it brings much to the table other than basic comms, so if you have an easier way to establish that, it's kinda meh.By the way, I don't know what "affordable" means, but I like the GPP4323 a lot. It has a load feature, too, which is super convenient for battery analysis.

author: alm
author_rank: Super Contributor
timestamp: March 15, 2024, 05:59:17 pm
content: Quote from: djacobow on March 15, 2024, 05:13:28 pmWhat (Py)VISA brings to the table in my opinion is that it makes it easy to switch communication method without changing the code. For example if a DMM has both USB and LAN ports (or two different DMMs), and you want to switch from one to the other, it just involves changing the connection string.Back before PyVISA was a thing, I first tried writing code that could use either GPIB or RS-232, but it was ugly. So I ended up writing a wrapper around PySerial that had the same interface as the GPIB module. Which is basically what VISA does.I agree it's not very compelling if you only use one type of interface.