EEZ Bench Box 3 - Sequel to EEZ H24005 - Page 1
Forum section: electronics / general

author: chriswebb
author_rank: Unknown
timestamp: July 11, 2019, 07:46:27 pm
content: Thought this forum would be interested in the latest product about to launch from the people who did the EEZ H24005 bench power supply:QuoteLink to the crowd supply.EEVBlog forum launch thread around the H24005here.

author: Kean
author_rank: Unknown
timestamp: July 12, 2019, 01:22:04 am
content: I have a couple of the H24005, and this new design looks quite good.Ethernet connection should be on the rear panel IMHO.Maybe they'll make an SMU plug-in - that would be cool.

author: Rerouter
author_rank: Super Contributor
timestamp: July 12, 2019, 01:29:48 am
content: Kean. If you have thoughts on how your would implement an SMU plugin. I'm willing to lay it out. Been working piecemeal on making a 4 quadrant output stage but I am limited in knowledge as far as making it accurate enough for SMU level use cases.

author: Kean
author_rank: Unknown
timestamp: July 12, 2019, 04:27:01 am
content: Quote from: Rerouter on July 12, 2019, 01:29:48 amNot really. I had dabbled with a design, but the precision I was aiming at was quite low.I'm not expecting anything like the performance of a Keithley 2400 of course, but something 4 quadrant and uA or better resolution.There is the EasySMU reference design/evalutation board from AD, but it is somewhat limited with only ±12V/±40mAStill many occasions I think I'd find that useful. Of course, there is no stock anywhere of the required eval board.https://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/dc2591a.html#eb-overviewMarco Reps was working on an open source SMU design called OSMU, but development on that seems to have stalled. Not sure what his planned specs were.

author: Rerouter
author_rank: Super Contributor
timestamp: July 12, 2019, 12:23:10 pm
content: I would say dream for the keithley, but lets see how we can approach it economically, the main pain for me is I do not know what the input structure looks like on a SMU, I assume it is similar to an electometer but with higher bandwidth for most of the ranges, equally what voltage and current ranges are you expecting?So we have this, the keithely 2400 output stage, nothing hard or expensive to make, and can be made a lot more flexible by using switching preregulation to reduce the total power dissipation of the output stage, instead of using all those taps, just keep it working like a bootstrap supply to keep the op amp under low power while leaving headroom for the maximum bandwidth of the transient responseWatching Dave's teardown, things of note:5.5 digit 1uA range at the low end, for measureing, while having a 10nA output resolution so, what can we do to get close to that, e.g. maybe we have a 12-16 bit 1uA full scale range, its not impossible, just needs good layout and decent op amps. (ENOB means we probably end up closer to 3-4 digits)The keithley does use a switching supply to make its +-225V rails, we could just do it a little more modern. tracking instead of fixed for higher output wattageE.g. they use an AD847JN for the output op amp, in many ways that is a fairly rubbish op amp compared to what is available today. High bias currents, high offset voltage, only really has speed and gain going for it.The ADC converter is a multi-slope converter controlled by an FPGA, now from another thread on this forum, the base of operation and op amps required for solid operation does not seem expensive, getting it to play nice over multiple decades of input may be harder, and this is where I would currently struggle, As I would probably be more willing to throw it at a self contained ADC chip, and focus on an analog control loop and managing gain with op amps.I suppose the multislope does gain you an integrator stage, the easier way to do device power measurement would be to measure the integrator voltage set to a suitable range to get the mA from the integrated mAh allowing the measurement that so many EE's seem to struggle with when devices have uA sleep currents mixed in with mA active currents. just at X samples per second sum to bring the integrator to 0V and measure the charge to cancel, this will give you a wide range device power consuption.Again throw some thoughts out, the man behind this project is very good at switching converters, so we may just need to step in to guide the linear and measurement side.

author: prasimix
author_rank: Unknown
timestamp: July 12, 2019, 09:52:05 pm
content: Oh, it seems that party started here without me. Thanks @chriswebb for opening this topic and others for followed up.Quote from: Kean on July 12, 2019, 01:22:04 amYeah, it's not simple at all to keep wire harness (checkhere) to lowest possible level, minimize PCB dimensions (especially the MCU board that has 4-layers) and have all things on the right places. I was thinking a lot, what to do, and for start I'm very satisfied with minimizing AC wiring (and soldering) to the minimum: currently only AC cables are what connect AUX-PS board (where soft-start/standby control is placed) and AC/DC power modules.Also I'm strongly believe that Ethernet (e.g. wired connection) should be an integral part of such kind of equipment, and that is better to have it on front panel then to remove it completely or replace with wireless. One can argue that we already have (wired) USB, but we have more ambitious plans for it that I believe will be soon in position to present.Quote from: Kean on July 12, 2019, 01:22:04 amRight, and as the first step in that direction I'd like to build a bidirectional 2-quadrant power module. Then support for all four should follows naturally, and of course we have to expand existing software/firmware that decent SMU functionality would be possible.

author: Teichhermelin
author_rank: Regular Contributor
timestamp: July 14, 2019, 10:28:36 am
content: Nice Idea

author: Zucca
author_rank: Unknown
timestamp: July 15, 2019, 12:15:19 pm
content: Subbed. I keep my eyes on you. The modularity is a must.Some SMU homework to read for inspiration, K2400:https://www.eevblog.com/forum/testgear/keithley-2400-sourcemeter-review-and-teardown/https://dev.xdevs.com/projects/kei2400/repository/raw/service/Keithley%202400%20Service%20Manual.pdfLast week I was just talking with a Keysight Engineer regarding the N6700 SMU Module1) The burden voltage for the current measurement is almost 0V2) The current range switch very fast without losing any data, AKA "Glitch free" (it can analyze the power spike if a device goes out from sleep mode).It seems there is a lot of demanding right now regarding a DC power supply which can assit the design of low power eg. IoT devices.I would more than happy to see a module to have not more than 20W of power but can do something like (best case of course!):QuoteHere also the feature to simulate a Li-Ion battery could be handy (it could be just software jazz.....)I can only suggest to have in mind the low power design process.PS: Also a 100W DC electric load module would be fantastic, with some feature to analyse battery discharge process.Now back to work, I have something to finish up.

author: prasimix
author_rank: Unknown
timestamp: July 15, 2019, 12:24:28 pm
content: Quote from: zucca on July 15, 2019, 12:15:19 pmI'd like to learn how "very fast" is really fast: do we talk about something in a range of microseconds, tens, hundreds (or more) microseconds?

author: Zucca
author_rank: Unknown
timestamp: July 15, 2019, 01:31:32 pm
content: Quote from: prasimix on July 15, 2019, 12:24:28 pmI asked the very same question. He told me something like:"The two current ranges are always on, you don't switch from one to the other, you just switch what you display"

author: exe
author_rank: Unknown
timestamp: July 15, 2019, 02:15:34 pm
content: Quote from: zucca on July 15, 2019, 01:31:32 pmTo me it sounds like there are two power supplies in parallel, the lower range has slightly higher voltage. When a current spike occurs, the first power supply saturates and drops voltage (CC mode), then second starts working. But that's just a guessSomething like this:https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=520808&nid=-11143.0.00&id=520808("Learn to connect power supplies in parallel for higher current output").UP: relevant video:

author: prasimix
author_rank: Unknown
timestamp: July 15, 2019, 02:55:00 pm
content: Hm, that makes more sense the using multiple resistor's based current sense. If current sense resistors are used you have to switch in one moment of time from one to another, or in case of just two ranges you can bypass low-range (high resistance) shunt with MOSFET switch that is connected in series with hi-range shunt. Switching speed is finite, it could be in a range of microseconds or perhaps less, but still more then zero.So, the existing H24005 and new BB3 (with two DCP405 power modules inserted into slot #1 and #2) can be under firmware control coupled in parallel (using internal power relay!) and it should be possible to add in firmware such "auto-ranging" mode of operation that user don't need to think a lot about settings, and proper measurement will be presented on the screen (or send to PC).

author: Zucca
author_rank: Unknown
timestamp: July 17, 2019, 01:46:28 pm
content: how funnyhttps://www.eevblog.com/forum/testgear/iot-power-profiler-and-battery-life-estimation/msg2553039/#msg2553039

author: prasimix
author_rank: Unknown
timestamp: August 24, 2019, 12:44:56 pm
content: A brief preview of new user interface on 4.3" TFT touchscreen display driven directly by STM32F7 and created using open source EEZ Studio:

author: prasimix
author_rank: Unknown
timestamp: September 11, 2019, 07:25:25 am
content: I've received yesterday small batch of cardboard transportation boxes for BB3 kit:... when assembled it looks like this:Additional small box is used for packaging three basic modules:Everything packaged: peripheral modules with AC/DC power modules come in the middle, small box with basic modules goes below. The main box has additional envelope for improved strength and for easier handling with all parts inside the box:

author: Rerouter
author_rank: Super Contributor
timestamp: September 11, 2019, 07:49:54 am
content: Now just waiting to buy one of these,Any ballpark on what a box and 3x 405's would run?

author: prasimix
author_rank: Unknown
timestamp: September 11, 2019, 08:28:55 am
content: We're trying to provide a 2-channel version (2 x DCP405B) in a same price range as previously backed H24005 at least for the early birds (all who are subscribed to the campaign will receive notice about exact start time in advance).Ok, the question is what is more interesting for the users: DCP405 or DCP405B model? The same PCB will be used for both, but thelatercomes without the following features:Down-programmerRemote sensingRemote programmingHW OVP (with triac crowbar and fuses)

author: Rerouter
author_rank: Super Contributor
timestamp: September 11, 2019, 08:31:21 am
content: I'm after the DCP405's

author: prasimix
author_rank: Unknown
timestamp: September 11, 2019, 08:33:14 am
content: Quote from: Rerouter on September 11, 2019, 08:31:21 amYeah, it's a "Full Monty", but more costly.

author: exe
author_rank: Unknown
timestamp: September 11, 2019, 11:10:40 am
content: How useful is downprogrammer? Do you have any oscillograms?Is it going to be a kit, or pre-assembled device? Do I need to solder anything? I like soldering.

author: prasimix
author_rank: Unknown
timestamp: September 11, 2019, 11:25:30 am
content: Quote from: exe on September 11, 2019, 11:10:40 amYes, we have:https://www.envox.hr/eez/eez-bench-box-3/eez-bb3-measurements/dcp405-power-module.html#dcp405_dpUsually people are not aware of such thing, but I hold from the very beginning that is an important ingredient. It does not just discharge Cout(that is very small in our case) but also Cinof the connected devices when set voltage goes down or OE (output enable) is switched off.Quote from: exe on September 11, 2019, 11:10:40 amIt will be an ARTR (almost ready to run) kit as the previous project. Therefore, you'll need just a Philips screwdriver and about an hour or your work following assembly instructions (as an example you can checkherehow it looks like for the previous project). Initial firmware version will be also included.Makers who like soldering, can choose a set of bare PCBs and custom enclosure. Also, you can buy DCP405B module and populate it missing parts to get DCP405 since BOM is published on the GitHub. Perhaps another possibility is that you pledge only the entry level unit that comes with assembled and tested three main modules (i.e. AUX power, MCU module and BP3C backplane) and try to assembly power modules manually.

author: prasimix
author_rank: Unknown
timestamp: September 11, 2019, 11:28:20 am
content: Oops, the link published above to the measurements include just picture of the output without down-programmer (don't know when the other one disappeared)Give me a moment to refresh that page...EDIT: Ok, Fig. 17 is now added. Feel free to check also Fig. 4 when huge capacitive load is connected on the output: it needs about 20 ms to discharge 2200 μF charged on 30 V.

author: Rerouter
author_rank: Super Contributor
timestamp: September 11, 2019, 11:40:55 am
content: Down-programming makes the output behave like a 1.5 quadrant output, able to source or sink current, (much weaker sinking, and unsure if current limited while sinking)when you have 2 outputs that can source or sink independently, suddenly you have a poor mans Source-Measure Unit, Its still not as nice as the real thing, but it gets you to a point where you can start recording meaningful data.Also lets you do weird things like using it for a low burden voltage milliammeter with other devices,I am far to used to bodging things in weird ways....

author: exe
author_rank: Unknown
timestamp: September 11, 2019, 11:53:44 am
content: If it can sink current, and I can set how much current it sinks, then I'd really want to have it.What's the sinking capability?

author: prasimix
author_rank: Unknown
timestamp: September 11, 2019, 12:30:54 pm
content: The sink capability can be calculated using the following equation: Isink, max= (VZD2- Vth) / R30 (See schematicshere, Sheet 3of6). Therefore for the current setup, and if we use as average Q5's Vthof 3 V it is (9.1 - 3) / 2.2 = 2.78 A. This is a huge current, but it last in milliseconds (previous down-programmer offered about 0.3 A).