hybridfree/eevblog-posts huggingface dataset:
RS-485 with Modbus vs CAN Bus - Page 1
Forum section: electronics / projects

author: Red_Micro
author_rank: Regular Contributor
timestamp: March 04, 2021, 04:54:53 pm
content: At a high level I know some of the advantages/disadvantages and differences of both RS485-Modbus and CAN Bus. In this post I just would like to read opinions based on people's experiences. Under which conditions or application you would choose a protocol over the other?

author: H.O
author_rank: Frequent Contributor
timestamp: March 04, 2021, 05:20:48 pm
content: Having used MODBUS RTU a bit but never CAN I won't call myself an expert but I know that CAN is a multimaster protocol and MODBUS RTU (or ASCII for that matter) is not which means MODBUS would be out if the application wasn't suitable for the master-slave type aproach that MODBUS uses.

author: max_torque
author_rank: Super Contributor
timestamp: March 05, 2021, 07:05:14 pm
content: The significant diffence is that CAN includes message collision avoidance and prioritisation/arbitration at a HARDWARE level. RS-485 does neither, so it is up to a Master device to schedule the bus timing and loading, whereas with CAN no master is required, and each device on the bus is able to simply transmit it's message at any time (although it is up to the bus architect to ensure that there is sufficient spare capacity on the bus, using suitable message prriorities to ensure that all devices get their fair share)

author: Renate
author_rank: Super Contributor
timestamp: March 07, 2021, 10:18:47 pm
content: Single master, use Modbus. Any µC with a UART can do it.Multiple masters/asynchronous alarms, use CAN. You'd probably want to use a CAN chip.
RS / Jackcon capacitors ?  - Page 1
Forum section: electronics / projects

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: June 12, 2016, 10:33:04 pm
content: I bought some 10000uF 50 V 105°C electrolytic capacitors under the brandRSpro from RS components.In fact, these are Jackcon LHK capacitors.This rises 2 questions :- Are all the electrolytic capacitors under the RSpro brand in fact Jackcon capacitors ?- Are these Jackcon capacitors OK ?Thanks

author: chris_leyson
author_rank: Super Contributor
timestamp: June 12, 2016, 11:24:53 pm
content: RS PRO, is a brand name made up by RS to sell cheap parts sourced from the far east. Buy the same part six months or a year later and do you have any guarantee that it will be the same part, no. Farnell do the same except it's called Multicomp. Draper is another brand name for cheap tools...and so on.I wouldn't design any of this crap into a product as you have no guarantee as to the source. As for Jackcon capacitors go check their website and look up the spec. They might be OK for prototyping or hobby use but for long term 5 or 10 years product life specify and buy from a well known manufacturer.

author: ZeTeX
author_rank: Frequent Contributor
timestamp: June 13, 2016, 01:16:57 pm
content: Jackcon in a nutshell is crap, they are not better then ChongX or what ever their name is.

author: Zero999
author_rank: Super Contributor
timestamp: June 14, 2016, 08:04:29 am
content: Yes, I avoid RS Pro and Multicomp, unless it's just for prototyping.

author: dmills
author_rank: Super Contributor
timestamp: June 14, 2016, 10:55:51 am
content: Been burned too many times by parts from both or those brands being designed in by others then going on long lead time (Multicomp inductors can be especially annoying this way).Regards, Dan.

author: wraper
author_rank: Unknown
timestamp: June 14, 2016, 11:02:16 am
content: Under RSpro or Multicomp brand you often get decent parts which otherwise cost 2-3x at the same distributor but that is a hit and miss. No guarantee that next time you will get the same part. Often you can check brand modified datasheet and figure what actual part you will get.
R&S Powersupply HMC8042 schematic or servicemanual ? any one ? - Page 1
Forum section: electronics / projects

author: oz2cpu
author_rank: Frequent Contributor
timestamp: March 18, 2022, 10:45:34 pm
content: this one is driving me crasyhow the darn heck does the voltage measure and feed back and pwm regulator work ??one channel is working perfectly..the other one read no feedback, so it assume output is zero and this way it try to kill it self trying to deliver the wanted output,at maxed out pwm, over voltage of 75V kills caps rated 50V, killed FET and fet driverhere is a videohttps://youtu.be/NLKiNW1-DDY
RS Pro panel brake resistors.... any idea on spec for self inductance? - Page 1
Forum section: electronics / projects

author: peteb2
author_rank: Regular Contributor
timestamp: January 29, 2020, 05:17:57 am
content: Just looking at a wee load project calling for minimal as possible inductance of the device but a cannot find a confirmation or spec for this parameter. Have fired off a request for further info, The datasheet specifies a wirewound technology so that would likely say a self inductance.All i need is a quick acknowledgment of whether they're non-inductive, somewhat inductive or very inductive, the latter two quickly sorting them as not suitable... (Perhaps someone else has already done a test)....I'm looking specifically at part-code 185-2445. Any input truly appreciated....
RS Pro vs Mean Well vs TDK Lambda embedded switching supplies - Page 1
Forum section: electronics / projects

author: bd139
author_rank: Super Contributor
timestamp: December 30, 2017, 10:31:14 pm
content: Need a couple of 24V 4.5A switching supplies for a project I'm working on (HF PA). One to use and one spare. This is going to be followed by a couple of Pi filters to reduce noise and a mains filter (Schurter IEC socket based one) on the front end. This is lighter and considerably cheaper than an equivalent linear supply.Is there a massive quality difference between generic supplies (not eBay, bought from RS in UK) and branded stuff from TDK Lambda?Pricing is £21 ex for an RS Pro (which looks like a Mean Well) and £30.40 ex for a TDK Lambda so 44% more.Going to buy one and test.The PA is going to be housed in a separate box inside the chassis to the PSU as is the TX/RX switching.

author: Someone
author_rank: Super Contributor
timestamp: December 30, 2017, 10:43:04 pm
content: Quote from: bd139 on December 30, 2017, 10:31:14 pmThere can be, it really depends on which parameters are important to you. Output noise can be radically different between manufacturers or series and reliability etc. But high prices aren't the only indicator so its best to test for your particular application.

author: nctnico
author_rank: Super Contributor
timestamp: December 30, 2017, 10:46:42 pm
content: My experience with Meanwell switching power supplies has been very good when it comes to reliability. It is my go-to brand.

author: bd139
author_rank: Super Contributor
timestamp: December 30, 2017, 10:54:24 pm
content: Thanks both.They come out on paper the same with output noise/ripple so I will grab a mean well and see what happens

author: dmills
author_rank: Super Contributor
timestamp: December 30, 2017, 11:21:37 pm
content: RS Pro is the RS equivalent of Farnells Multicomp, which is to say whatever was cheap by the container load this month. I avoid both on general principle.I have had surprisingly good luck with Meanwell (Got a few hundred out there, never seen a failure), for all that TDK is still my go to brand when the cash does not matter.Regards, Dan.
RS232(?) Data port on cheap Chinese caliphers/comparators - Page 1
Forum section: electronics / projects

author: silenter
author_rank: Newbie
timestamp: June 14, 2019, 03:25:31 pm
content: Hi everyone. I bought a long time ago one of those cheap chinese comparators that you can find off ebay:https://www.aliexpress.com/item/RS232-9holes-data-output-for-digital-indicator-electronic-indicator-data-output-link/1227581712.htmlArguably this thing has a data port, but it came without a cable and I would like to get off some readings.There's not much I could find about the 4-lead port and/or the connector. They mention rs232, but I assume it's just about the bundled adapter.Before I spend some time on it (I would probably just solder 4 wires directly on the tracks), has somebody already tried to look into it and knows what sort of pinout/protocol is it?

author: sokoloff
author_rank: Super Contributor
timestamp: June 14, 2019, 03:34:49 pm
content: You're not the first to try this, of course.Have a look at:https://www.robotroom.com/Caliper-Digital-Data-Port.htmlhttps://hackaday.com/2010/12/15/reading-a-digital-caliper-with-a-microcontroller/https://www.instructables.com/id/Reading-Digital-Callipers-with-an-Arduino-USB/

author: SparkyFX
author_rank: Frequent Contributor
timestamp: June 14, 2019, 04:05:53 pm
content: check out TouchDRO, there are descriptions of the protocols found in various calipers.
RS232 line drivers on powered down devices - Page 1
Forum section: electronics / projects

author: ChristofferB
author_rank: Frequent Contributor
timestamp: December 19, 2015, 03:13:17 am
content: Hey! So I've been working a lot recently with a small 8051 single board computer, which features the MC1488 and MC1489 RS232 line drivers, and I have it connected to a PCI serial card in my PC.Now, the trouble is, RS232 has its transmit line driven lo (like, -12V) when it's idle.So what would happen if you powered off the board, both 5V and +-12V rails, but left the serial plug in?It'd be nice not having to disassemble the setup every time.So can the MC1489 handle RS232 voltages while powered down?And can the MAX232 devices, by the way?Thanks in advance,Christoffer

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 19, 2015, 05:27:38 am
content: RS232 transceivers are designed to withstand the inputs being driven when powered off.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: December 19, 2015, 12:38:33 pm
content: Great, well then, that's solved!Thanks!--Christoffer
RS232 logic voltage levels - Page 1
Forum section: electronics / projects

author: Vicky123
author_rank: Newbie
timestamp: November 20, 2013, 06:57:29 am
content: Hi All,I want to interface an SoC to a Sensor Board through RS232.The Soc has RS232 which is 3.3v( not in data sheet, Measured on my own).The sensor board has standard 5v RS232( measured voltage is -8.5v , I think its correct as it can have +12/-12 right?)Can I connect these two interfaces? If not, why? and what can be the solution?Thank you.

author: macboy
author_rank: Super Contributor
timestamp: November 21, 2013, 03:37:53 pm
content: RS-232 is a physical transfer medium (think OSI layer 0 if you are familiar with that) for UART commumications. The UART would be like layer 1.RS-232 specifies voltages of -3 to -15 volts for a '1' bit, and +3 to +15 volts for a '0' bit (up to -25 or +25 volts under EIA-232 standard). Note that the polarity is inverted.The UART device itself usually operates at TTL levels, with a '0' bit being around 0 volts (0 to 0.8 V) and a '1' bit being around 5 volts (over 2.0 V). Generally a driver chip or chips like a MAX232, or the MC1489/1488 pair are used to translate the TTL levels into the high voltage, inverted, RS-232 levels.A UART idles at "1", so at TTL levels, that is "hi" voltage (over 2V), and at RS-232 levels, it is the "low" voltage (-3 V or greater).If you have measured -8.5V at the sensor board, it is using RS-232 levels. Your SoC seems to be using TTL levels. The easy way to interface them is a MAX232 or similar chip (there are many clones and variations from many manufacturers). You could also build a level-shifting inverter with transistors, but you'll need +/- 12 V (or so) supplies. The MAX232 generates its own HV supplies from +5V. You can buy a board with MAX232, DB9 connector, and jumper wires on ebay for a few $ (likethis- no affiliation)

author: Andreas
author_rank: Super Contributor
timestamp: November 21, 2013, 09:17:48 pm
content: Quote from: macboy on November 21, 2013, 03:37:53 pmThe +/-3V specification is at the receiver.The transmitter has to deliver minimum +/-5V into a 3-7 kOhm load. (5kOhm nominal).Witin a 3.3V supplied system I would use a MAX3232 which is specified for 3.3V operation.With best regardsAndreas
Anyone Know of a RS232  Serial Logging Program that is Configurable for Parsing? - Page 1
Forum section: electronics / projects

author: LaserSteve
author_rank: Super Contributor
timestamp: October 01, 2021, 04:08:19 pm
content: A student at work has brought me a simple sensor that uses RS232 challenge - response for its protocol. Anyone know a good serial logger program that can send a few bytes and then read it out the return / strip a checksum, and save the raw string as as Excel or CSV on a PC?Part of a much larger project and I'm too busy right now to code.I should clarify, I have the Gymnasium sized Undergraduate Pilot Plant tore apart for it's 20 year annual rebuild, usually done once in the career of the Departmental Technician. A three story 1960s chemical plant made of entirely Pyrex glass, 316 Stainless pipe, and Teflon seals requires special attention. None of the parts are commercially produced any more, so much lathing, threading, welding, and glassblowing is going on. As is the quest to get funding approved for repairing each new glitch or corrosion spot found.Four meter sections of 12 cm ID glass pipe, coupled with flanges, TMEG seals etc. etc. So the needs of 330 students next semester outweigh my desire to help one gifted student this semester.. Otherwise I'd code this and help her learn the coding process. Hint: She's not a EE... Some how Chem Eng skips coding other then Excel / Matlab / Chemcad...Sensor She chose is pretty cool...https://sandboxelectronics.com/?product=mh-z16-ndir-co2-sensor-with-i2cuart-5v3-3v-interface-for-arduinoraspeberry-piI'll wire her a USB to Serial converter at lunchtime.Wireshark, perhaps? I've never used it.Steve
rs3232 serial to TTL Cap question ? - Page 1
Forum section: electronics / projects

author: Cj1corbystarlet
author_rank: Contributor
timestamp: October 13, 2011, 01:19:17 pm
content: Hi guy's and Gals,I'm doing a typical serial to TTL project based around a rs3232 chip, Looking at the data sheet i can use 0.1uf caps(5 in total) since i'm only working with 3.2v, ok got that, the caps are polarised in the data sheet for the chip.What type of cap should i use ?? Tant/monolithic/ceramic/whatever...... i have a bag of ceramics laying around (non polarised) will they do the job.Yes a retarded question, but its doing my head in.regardsBen

author: deephaven
author_rank: Frequent Contributor
timestamp: October 13, 2011, 01:37:57 pm
content: They will be just fine.

author: daedalus
author_rank: Regular Contributor
timestamp: October 13, 2011, 02:49:43 pm
content: Ceramic will be ok, but their voltage rating should be higher than 15v, as the chip will act as a charge pump to drive RS-232, and rs232 levels are anywhere from 5v to 15v (the spec goes to 25v, but that's pretty much unheard of these days).

author: Unknown
author_rank: Unknown
timestamp: October 13, 2011, 04:15:00 pm
content: It depends on the driver. I think the MAX3232 uses voltage doubler, so peak level should be ~11V max. The average is just above 5V.

author: Cj1corbystarlet
author_rank: Contributor
timestamp: October 14, 2011, 12:09:12 am
content: Thanks all for the replies, the ceramic caps i have are a 50v rating, and the rs232 data is at 5v,regardsBen
RS422 terms at both ends? - Page 1
Forum section: electronics / projects

author: bitbanger
author_rank: Regular Contributor
timestamp: August 26, 2019, 02:24:27 pm
content: Under what circumstances would one want to parallel terminate both the TX and RX ends of a 422 network with 120ohm? I see this referenced every once and a while. Is the hope to diminish reflections at both ends? Does this not inherently conflict with matching cabling characteristic impedance of ~100-120ohm?One example:http://www.interfacebus.com/Design_Connector_RS422.html

author: rstofer
author_rank: Super Contributor
timestamp: August 26, 2019, 03:56:56 pm
content: See Figure 4https://www.maximintegrated.com/en/app-notes/index.mvp/id/723From the point of view of the master, the transmit pair are terminated on the far end and the receive pair on the near end.

author: David Hess
author_rank: Super Contributor
timestamp: August 26, 2019, 04:43:56 pm
content: For bidirectional operation, the transmission line is terminated at both ends. The RS-422 transmitter only sees the near termination as an additional load. The termination on the far end from the transmitter is the one which matters.This is also why transmitters in the middle do not require any termination on their output at all. They see two parallel transmission line loads and both end terminations absorb reflections.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 26, 2019, 11:04:41 pm
content: 422 is always-on so the transmitter impedance is already very low (typically less than Zo) and so you're only wasting power and range while doing nothing for reflections.485 has an enable so there may be some value in terminating the transmitter -- namely if it's at the end of a line as mentioned above.Tim

author: bitbanger
author_rank: Regular Contributor
timestamp: August 27, 2019, 12:51:53 am
content: Sorry perhaps I should have been a little more clear. In the included link, they provide calculations for fail-safe resistor network. The calculations seems to imply that on a single pair, from TX to RX, you would have 120ohm on each end of the pair. No matter multi-drop or not, each RS422 pair is still considered "one direction", there is no TX enable like 485, so I don't see the point in terminating both ends.
RS485 full duplex - Page 1
Forum section: electronics / projects

author: richcj10
author_rank: Unknown
timestamp: November 22, 2014, 04:48:33 am
content: I am using the LTC2863 driver and it doesn't have driver enable pins broken out. I was wondering if it is needed for multi slave bus?

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 22, 2014, 05:40:13 am
content: I can't see how you could implement a multi-drop bus with that chip.That version appears to be intended for simplex, point-to-point applications.If you have more than one transmitter, you must be able to disable them except when transmitting.

author: richcj10
author_rank: Unknown
timestamp: November 22, 2014, 06:13:53 am
content: What is the right set up for something like this?

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 22, 2014, 06:52:15 am
content: Assuming by "multi slave bus", you mean a bus with more than one transmitter, you must be able to disable all the transmitters except when sending data onto the bus. That would preclude the LTC2863 variety. But all the other varieties have the enable feature, so you must use a different chip.
RS485 Modbus - LG Heat Pump - Page 1
Forum section: electronics / projects

author: Blackgar
author_rank: Contributor
timestamp: December 11, 2022, 12:05:23 pm
content: Hello everyone,I am building a project to read some values through modbus from my LG HM161M U33 heat pump.The pump is by default master so I just enabled thought the thermostat the meter function (tries to communicate with an external slave device with 0xB1 address) in order to see the packets on the modbus and check the bus settings.So I just used an USB-RS485 converter to capture the packets. So I verified that the settings was:9600-8N1By these settings and by setting the pump as slave (using the SW1:1) I tried to send some commands to the pump but no answer back. The pump slave address was set to 0x01 through the thermostat. Some of the command I tried:01 04 00 00 00 08 F1 CC01 03 00 00 00 02 C4 0BIs there any chance the settings for slave being different than master?
RS485 PWM controller  - Page 1
Forum section: electronics / projects

author: richcj10
author_rank: Unknown
timestamp: January 28, 2013, 12:18:33 am
content: I am using a ATmega328P uC with a TLC5940 (Used in a PWM Mode w/ pullups).I use a MAX485 chip to receive the serial commands. It works well with most motor controllers and all servos.The one motor controller it doesn't work is the Vector Motor Controllers. I can't figure out why they don't like the signal(They think that the signal isn't there). Attached is the schematic of the system. Any suggestions would be great!Thanks,Rick

author: Kremmen
author_rank: Super Contributor
timestamp: January 28, 2013, 06:55:59 am
content: Be more specific, please. What serial commands? Which protocol? What vector controllers? What commands?

author: richcj10
author_rank: Unknown
timestamp: January 28, 2013, 07:24:34 am
content: The board receives speed commands via a serial stream over RS485. The board sends out commands to the motor controllers via PWM.This device (ATmega328P) handles logarithmic ramping / updating / and safety shutoff.The motor controllers in question are the IFI VEX Pro Victor 88x. I like these because of there rigidity for there price points.But the draw back is they are very sensitive to the signal coming into them. They like to go into a fault condition representing a bad or no signal.I have gotten them to work with a output Compare peripheral on a AVR.

author: amyk
author_rank: Super Contributor
timestamp: January 28, 2013, 08:48:10 am
content: How about some scope/LA screenshots? Have you tried inspecting the signals?
RS485 read data from fingerprint slave device - Page 1
Forum section: electronics / projects

author: tozoysa
author_rank: Newbie
timestamp: February 14, 2017, 01:01:54 pm
content: Hello,I have purchased a fingerprint slave module thinking that i could read the output of the module and process it by myself via a microcontroller. The module i purchased has only RS485 interface. Wonder if i could read the output using RS485 to TTL convertor(Maybe using arduino serial monitor, or teraterm perhaps?) using this module?Fingerprint slave module :https://www.alibaba.com/product-detail/HF-F12-Fingerprint-and-ID-Card_60355134367.htmlRS485 to TTL convertor :http://www.ebay.com/itm/272351498314?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT- I'm still waiting for this to arrive thoughPlease advice!Thanks in advance!Regards,Prasad.

author: ajb
author_rank: Super Contributor
timestamp: February 14, 2017, 05:51:37 pm
content: That will probably work, as long as the reader only uses a single half-duplex pair. If it uses separate Rx/Tx pairs you'll need a second transceiver. RS485 is just an electrical specification, though, so you'll need to know what sort of data format the reader uses. It's probably a simple UART protocol, but at the very least you'll need to find out what baud rate, parity type, and number of stop bits the reader uses. Beyond that, you'll need to know how the data is structured and transmitted, which can vary quite widely.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 14, 2017, 05:59:25 pm
content: Quote from: ajb on February 14, 2017, 05:51:37 pmThat would be RS422

author: ajb
author_rank: Super Contributor
timestamp: February 14, 2017, 07:34:55 pm
content: Quote from: mikeselectricstuff on February 14, 2017, 05:59:25 pmYes, but I wouldn't be too quick to trust most non-specialist vendors to make that distinction, let alone some random alibaba seller...

author: CM800
author_rank: Frequent Contributor
timestamp: February 14, 2017, 09:08:06 pm
content: Quote from: ajb on February 14, 2017, 07:34:55 pmYes, I will say RS422 / RS-485 is used pretty interchangeably, even in the motion control industry. I've been prodding various suppliers to correct it for some time!
RS485-RS232 issue and strange IDLE. - Page 1
Forum section: electronics / projects

author: Sudo_apt-get_install_yum
author_rank: Regular Contributor
timestamp: June 23, 2025, 02:04:54 pm
content: Im unsure of what is going on regarding my RS485 communication....I have a master device that communicates with a slave device (Polling based).Master sends the data. The slave receives, parses the packet and responds. I've made several different slaves with different functionality and all function but one design.The IDLE level seems to be inverted witch should be the result of inverting the A & B channels or very wrong fail-safe termination.But the slave communicates fine when directly connected to a USB-RS485 adapter and the signal & IDLE levels are correct...I have no clue as to why...I've removed the fail-safe termination, almost no change in signal.I've adjusted the differential termination, no noticeable change.Swapped A & B, did not work. As expected.As one can see in the images is that the data is unchanged from the master RS485-RS232 RO output to the MCU input. And that the data directly from the masters RS485-RO output is not the same as the data on the bus itself.Specs:Speed: 9600 b/sHalf-DuplexMaster: ST485EBDRSlave: SP3485EN-L/TRFirst packet is the master request, followed by the slave response. First image is directly from the RS485 A-channel.

author: PGPG
author_rank: Frequent Contributor
timestamp: June 23, 2025, 03:53:14 pm
content: At MCU input you probably should have stable state = 1 (hi) and start bit should be 0 (lo state).Check how MCU output looks like when it sends data.

author: Sudo_apt-get_install_yum
author_rank: Regular Contributor
timestamp: June 24, 2025, 06:25:48 am
content: Its pretty much what is expected.The Masters RS485 RO IDLE is inverted, but i have no idea why...See the below images.
RS485 - star topology - Page 1
Forum section: electronics / projects

author: ksrm
author_rank: Newbie
timestamp: June 09, 2016, 05:52:52 pm
content: I'm wondering if anyone has any experience with using RS485 in a star topology (i.e. several nodes connected directly to the master in the middle). I know this is not the 'done thing' but I'm just wondering if it can be done at all with a low enough bit rate and short enough stub length. We only need to query each node every minute for ~32 bytes of data so the baud rate can be super low. There would be around 5 nodes all less than 5 metres away from the master.Questions:Can it be done? Do I even need the termination resistors in this case? Do I need to use drivers with a slow transition time like the SN65HVD3082E, or is this irrelevant?If this sounds like a bad idea, is there any other bus more suitable for use in a star network?Any advice would be appreciated.

author: ajb
author_rank: Super Contributor
timestamp: June 09, 2016, 06:01:37 pm
content: Assuming a UART connection, a low enough baud rate will overcome some pretty egregious wiring. Lack of termination isn't a huge concern until the wiring length represents a substantial fraction of the symbol period. I've seen a number of setups in the hundreds of feet at 250kbaud unterminated and with suboptimal wiring and rarely if ever any problems short of actual bad cables/connections. A synchronous connection that is more sensitive to spurious clock signals may be slightly more delicate.

author: C
author_rank: Super Contributor
timestamp: June 09, 2016, 08:36:04 pm
content: The simple thing would be have a proper RS485 buss but with the wire path in shape of a Star. Wire from Hub out to device and back to hub.'Both ends of the RS485 buss is at the hub and can be terminated in hub.Down side is the RS485 buss is 2X long.Done correctly every thing else is easer to maintain, add or change.
RS485 using a multiplexer on A line - Page 1
Forum section: electronics / projects

author: metRo_
author_rank: Regular Contributor
timestamp: March 28, 2019, 12:03:39 am
content: The project I'm working on require communication between a master and 20 nodes at 115200 baudrate, the nodes will be align (Node1 - Node2 - NodeN) and separated from each one 50cm.QuoteThis guyimplemented auto addressing by controlling the RS485 lines.Can I use a mux like this one to control the A linehttps://pt.mouser.com/datasheet/2/916/74LVC1G3157-1318329.pdf? Should I apply a mux to both signals?thank you

author: rstofer
author_rank: Super Contributor
timestamp: March 28, 2019, 02:31:16 pm
content: If you are designing the slaves, why not implement a proper protocol?http://www.bdmicro.com/code/robin/QuoteWithout the multi-master approach things are even easier. Each slave has an address and unless the master started a conversation with the address, it doesn't talk on the bus. Both ends agree in advance to the length of the returned slave message. The slave needs to know when to shut up.This whole RS485 thing has already been worked out. No hardware multiplexor is ever used. Just a clean protocol describing the conversation between a master and an addressed slave.

author: ajb
author_rank: Super Contributor
timestamp: March 28, 2019, 03:17:12 pm
content: Quote from: rstofer on March 28, 2019, 02:31:16 pmThe OP is asking about a scheme to auto-assign station addresses to nodes on a bus, presumably such that the station addresses are mapped to the physical ordering of the bus.I've used a similar scheme, and it can certainly work. You should be able to use just about any analog switch, provided the cumulative resistance is not too high and the switch is sufficiently protected against harm. Another option is to run a separate IO line out from one node and into the next, so once the first node in the line is addressed it asserts the signal to the second one which starts its address negotiation, etc. I think mikeselectricstuff used this scheme on his massive wall of iPod LCD project. This can be just a regular digital IO--in fact RS485 is probably overkill for your serial link. For 115kbaud over 2m, you'd probably be just fine with regular TTL serial unless the environment is especially hostile.

author: metRo_
author_rank: Regular Contributor
timestamp: March 28, 2019, 05:18:04 pm
content: Quote from: ajb on March 28, 2019, 03:17:12 pmIt's 10m but the main reason to use RS485 is to have a bus and been able talk with each node individually. I thought on an IO line too but that will add another wire and if a node fails it could mess up the network. With a mux I'm thinking on have A and B normally connected and a device open the lines if doesn't have an address.Do you recommend a analog switch for this purpose?I found thisapp noteabout the use of AQY282S but it is expensive.
RSD Academy - Building a Linear Power Supply - Part 6 - Design Troubleshooting - Page 1
Forum section: electronics / projects

author: rsduhamel
author_rank: Contributor
timestamp: January 12, 2018, 05:33:32 pm
content: Here is my latest video on building a linear power supply. While making the previous videos I wasn’t getting the current output I expected. I planned to make a 12 volt, 4 amp supply, but my voltage started to collapse at less than 500 mA. In this video I test my design and components to find out why it isn’t working as planned.https://youtu.be/DpjQAp37n1UThis video series is not about how to build the best power supply. It is about learning how components work together to make a useful circuit. When finished I will have built, and explained in detail, a primitive but useful bench power supply. Thanks for watching.
RSD Academy - Using an Oscilloscope - Page 1
Forum section: electronics / projects

author: rsduhamel
author_rank: Contributor
timestamp: February 05, 2018, 04:20:03 pm
content: My latest RSD Academy video,Using an Oscilloscope - Oscilloscope Basics, is now live. It's targeted at people who are new to electronics so it's very basic. It starts showing how an oscilloscope is an analog voltmeter. Then it shows that an oscilloscope displays how voltage changes over time. It ends showing how to measure a wave's period and then calculating the frequency. Thanks for watching.https://youtu.be/m1YXkDskCAQ

author: Cliff Matthews
author_rank: Unknown
timestamp: February 05, 2018, 04:47:47 pm
content: Well done, nice use of measurement overlay and insert close-ups too. I would consider making a playlist for listing here:https://www.eevblog.com/forum/beginners/electronics-primers-course-material-and-books/
RTB 2004 Battery Mod - Page 1
Forum section: electronics / projects

author: sixtimesseven
author_rank: Frequent Contributor
timestamp: July 20, 2019, 09:08:43 pm
content: I was wondering if there is a project / mod adding a battery to the RTB 2004 oscilloscope?There is a lot of space in there and it would be very usefull to me. It would be pretty straight forward to do since the 2004 is supplied with a single 12V rail from the ACDC module... Perfect for a 3-cell Lipo replacement I think.However, why reinvent the wheel...

author: InductorbackEMF
author_rank: Regular Contributor
timestamp: July 20, 2019, 10:03:10 pm
content: Hi,I was thinking the same thing for the RTM3004 same single 12v rail.May be worth testing the power draw to get a feel of how long it would run with some Lipo cells.If you do go ahead please say so!Alex.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 21, 2019, 03:22:09 am
content: If it does require just 12V, a 3S pack with a BMS will indeed work nicely. Certainly easier than on other scopes such as my GDS-1062A that need several DC/DC converters.Someone modded a Rigol to run on batteries.https://www.eevblog.com/forum/chat/()-rigol-ds1052ed-power-supply-dc-voltage-add-battery-pack/

author: sixtimesseven
author_rank: Frequent Contributor
timestamp: July 22, 2019, 08:25:07 pm
content: Quote from: InductorbackEMF on July 20, 2019, 10:03:10 pmI measured the current drawn after boot up to be 3 A idle and 3.4 with all four channels enabled. Voltage is pretty spot on 12V. I measured 11.97V with my DM3068 meter.QuoteIndeed, just a single 12V rail. Nicly broken out from the shield and with a 4-Pin Molex which looks like a smaller version of the 4-pin ATX connector. Probably this one:https://www.molex.com/molex/products/datasheet.jsp?part=active/1053081204_CRIMP_HOUSINGS.xml.Thanks Rohde SchwarzEdit: Just found the power supply:https://www.digikey.ch/product-detail/en/xp-power/ECS65US12/1470-1296-ND/4487677Credit to Mike!

author: coromonadalix
author_rank: Super Contributor
timestamp: July 22, 2019, 10:30:09 pm
content: Tons of emptyness to play with ??

author: sixtimesseven
author_rank: Frequent Contributor
timestamp: July 23, 2019, 09:34:33 am
content: QuoteWould be plenty for my 4s 8000mA RC battery I have laying arount. To bad it is not 3s.
rtc- bios battery connector for NVDIA agx orin - Page 1
Forum section: electronics / projects

author: electronx
author_rank: Regular Contributor
timestamp: February 06, 2025, 07:58:41 am
content: I am looking for a connector compatible with Agx orin as seen in the photo, but when I looked at the Wieson America website, I could not see such a product.Interconnect (SMD) MALE Header RA 2 POS 1.25mmAC2651-0011-003-HHWieson America Inc.https://www.digikey.com.au/en/products/filter/rectangular-connectors/headers-male-pins/314?s=N4IgjCBcoGwJxVAYygMwIYBsDOBTANCAPZQDaIALAAxwUBMVIAuoQA4AuUIAyuwE4BLAHYBzEAF9CADimIQKSBhwFiZcHTABmOjGZtOkHv2FjJIOI2jy0WPIRKRymuDBgBWPSA5deg0RMI4CCsFJTtVRxBtMBg6TU9vQ18TAPAAdgs5UNsVB3IYKQpZFi8DIz9TQgBaOiyofgBXXLUPQOYzKoQQ%2Br4m%2BzUIJnEzDytWKDA2ccg6N2GgA

author: fchk
author_rank: Frequent Contributor
timestamp: February 06, 2025, 11:08:16 am
content: I would try Molex Picoblade.
RTC chips - DS1307 vs PCF8563 - Page 1
Forum section: electronics / projects

author: leonerd
author_rank: Regular Contributor
timestamp: January 11, 2016, 01:35:40 pm
content: I appreciate I'm likely asking a question similar to vim/emacs or AVR/PIC, but... Does anyone have any preferences?They're both 8pin SOIC-available chips running on 32kHz watch crystals and talk I²C, but they do appear to have differences.The DS chip has only one "output" pin that you can use for either squarewave or alarm interrupt, but does have a separate Vbatt pin.The PCF lacks a dedicated battery input (but you can mux main supply and battery with a couple of diodes), but in its place has separate "clock pulse output" vs "interrupt" pins. Also the PCF has a little timer unit almost like an AVR timer, with a prescaler available at 4096, 64, 1Hz or 1/60th Hz frequency, and an arbitrary 8bit counter.The two appear to be similar cost and similar board layout requirements. Anything else I should consider to prefer one over the other?Links:DS1307:https://www.maximintegrated.com/en/products/digital/real-time-clocks/DS1307.htmlPCF8563:http://www.nxp.com/products/interface-and-connectivity/interface-and-system-management/i2c/i2c-real-time-clocks-rtc/real-time-clock-calendar:PCF8563

author: AlxDroidDev
author_rank: Frequent Contributor
timestamp: January 11, 2016, 03:50:00 pm
content: Quote from: leonerd on January 11, 2016, 01:35:40 pmThat depends on your use. There is also the DS1337, which has 2 interrupts an no ext battery. The DS1337C goes a little further, not even requiring the external crystal.The choice depends on your project. What do you intend on connecting it to Do you need the backup battery?If you're working with AVR, keep in mind that there are several working libraries written for the DS1337 and DS1307.

author: theatrus
author_rank: Frequent Contributor
timestamp: January 11, 2016, 05:28:56 pm
content: Also a lot of processors these days have internal RTCs with distinct battery voltage rails - its a common occurrence on NXP and Freescale parts anyway. Those RTC chips are not the cheapest

author: leonerd
author_rank: Regular Contributor
timestamp: January 19, 2016, 01:47:26 pm
content: I have decided on the PCF8563 chip in the end. It just won out on the fact that it requires an external load cap, for which you can use a trimmer cap allowing you to calibrate it for extra accuracy, whereas the DS1307 has built-in internal caps. Also the more flexible clock out + separate interrupt pins might be useful to me.Thanks all.
RTC crystal thermal response and calibration - Page 1
Forum section: electronics / projects

author: sebmadgwick
author_rank: Regular Contributor
timestamp: April 28, 2015, 10:42:09 am
content: I just posted some information in another forum as part of a discussion but I thought it might also be of interest or use to people here. I collected some data to investigate the accuracy of a RTC crystal over a temperature range and test potential thermal calibration models.The plot below (Fig1 - Thermal response) shows the RTC crystal error of 8 devices over a temperature range. The parts were a dsPIC33 and a 20 ppm crystal.From this data, I was able to calculate the crystal characteristics shown in the table below (Fig2 - Crystal parameters). These values are close to the typical values defined in the datasheet (e0 = 20 ppm; c = 0.035; T0 = 25).I then wanted to determine the accuracy of temperature calibration models of various complexities. A calibration model would use the temperature measurement to estimate the crystal error which would then be compensated for in software. The following plots demonstrate the error of the above 8 crystals when compensated for each calibration solution.The simplest calibration model would assume the typical values define in the datasheet (i.e. assume every crystal is identical). This calibration model yields the crystal error shown the in the plot below (Fig3 - Calibration using typical values).A slightly more complicated calibration solution would be to use the same second-order model indicated by the datasheet characteristics but to use the actual characteristic values for each crystal as listed in the above table. This results in the crystal error show in the plot below (Fig4 - Calibration using actual values).The final calibration solution (most complex) would be to use the actual characteristic values for each crystal in a third-order calibration model. This results in the crystal error show in the plot below (Fig5 - Calibration using 3rd order). The large errors from below -15 degrees Celsius are due to unstable temperatures in the thermal chamber at the start of the experiment.I hope this is of interest or use to others.
RTC MAC Address? - Page 1
Forum section: electronics / projects

author: DrMag
author_rank: Regular Contributor
timestamp: September 14, 2016, 07:15:00 pm
content: I'm working on a project where I'm going to be using (for the first time) a real time clock. In researching various options, one of the devices that makes sense is the MCP7941x.This device comes in three variants: the MCP79410 has a blank EEPROM, the MCP79411 has a preprogrammed EUI-48 MAC address, and the MCP79412 has an EUI-64 MAC address.Perhaps my understanding of the MAC address concept is too limited--why would an RTC have any need of such a thing, as there's no networking capability on the chip? (It's a simple I2C connection, and they all have the same, non-configurable I2C address anyway.) Would I really have any reason to work with either the x11 or x12 devices as opposed to just the x10?I've been sifting through thedatasheet, but it seems to not mention the included MAC address at all aside from the fact that it can be included.

author: MosherIV
author_rank: Super Contributor
timestamp: September 14, 2016, 07:27:52 pm
content: Many ethernet phy/devices require non volatile memory to hold settings, so having some storage combined with rtc makes system costs lower.Some hobbiests want to be able to integrate their own ethernet interfaces but cannot afford the registration costs required to get a MAC address, so being able to buy a device with a pre programmed MAC address is quite clever.
RTC source voltage - Page 1
Forum section: electronics / projects

author: Chris3D
author_rank: Newbie
timestamp: December 23, 2018, 03:04:25 am
content: First, Happy Holidays to all!I'm making a small wrist watch for my son using an ATTiny841 and keeping time with an M41T62 RTC from ST, all powered by a single lipo cell. I'm trying to keep the component count as low as possible, and I'm wondering if the accuracy of the RTC will be affected if I power it directly from the battery vs. through a small voltage regulator.Powered from the battery, the voltage to the RTC will vary between 4.2v fully charged to ~3 volts. This is within the source voltage range of the RTC (1.3 to 4.4v). I just don't know if this will effect the RTCs accuracy vs. powering it through, say, a small 3.3v regulator so it always sees a steady voltage.If I could save the space on the PCB of the regulator and caps, that would be great, but if it's going to throw off the accuracy, I'll fit them in.Thanks in advance!-Chris

author: ataradov
author_rank: Super Contributor
timestamp: December 23, 2018, 04:26:17 am
content: No, it should not matter at all.

author: Dave
author_rank: Super Contributor
timestamp: December 23, 2018, 02:02:25 pm
content: The voltage doesn't matter much.What does matter is correct capacitive loading of the crystal. Make sure you read your crystal's and microcontroller's datasheets and use the correct value capacitors (preferably C0G ceramic type).It is also desirable to isolate the ground currents of the oscillator from the rest of the circuit, but that's just a minor difference.

author: Chris3D
author_rank: Newbie
timestamp: December 23, 2018, 04:35:02 pm
content: Thanks for the replies guys!I'm using the LCC8 package version of the RTC, which has an integrated crystal and related components, so I didn't have to worry about precisely matching those. That and because it's tiny!Here are boards I made for the RTC (right) and a 28 channel LED driver (left) I'll be using. I'm new at all this and just figuring it out as I go, so I make up small boards to test out new circuits and/or ICs before building them into something larger. So it'd be useful afterwards, I powered the RTC through a 3.3v regulator on the little board, but for the watch, not needing that or the backup supercap will save quite a bit of space. I'm trying to keep the watch as small as possible since my son is 9yo and he'd look funny with a giant circuit board on his wrist... or funnier than he'll already look with a circuit board on his wrist!
RTC - Page 1
Forum section: electronics / projects

author: electros6
author_rank: Regular Contributor
timestamp: May 26, 2014, 01:11:32 pm
content: Hi,I tried to use RTC in one my project.It works but the time is goon deviate about a minute in a day. I tried using DS1307 and MCP7940 but in same result. I used 30ppm 32.768Khz crystal as specify in the datasheet.I don't what is the problem please guide me.

author: dannyf
author_rank: Super Contributor
timestamp: May 26, 2014, 01:34:15 pm
content: QuoteLearn to get people to help you.

author: rob77
author_rank: Super Contributor
timestamp: May 26, 2014, 02:39:48 pm
content: "learn to ask for help" - provide the schematics and as much details as you can. no one know what is your circuit => no one can help you.but in general:with a 30ppm crystal you should get something like 2.5 seconds a day. so looks like your xtal oscillator is not working properly.i would suggest to add a capacitor trim pot instead of a fixed capacitor and tune it - use a counter to find the exact 32768 Hz.another approach would be to buy a ready to go and calibrated RTC module from DX or eBay

author: retrolefty
author_rank: Super Contributor
timestamp: May 26, 2014, 02:47:50 pm
content: I had variable accuracy using a couple of DS1307 with external crystals. One early module did have an adjustable trimmer cap that allowed me to tweak it for better accuracy. However these days I only buy the better quality RTC chips or modules that have an internal crystal with tcxo compensation. The chip costs more the the DS1307+crystal but in this case you get what you pay for.Here is an example on one that uses SPI interface rather then I2C but they are also available in I2C flavor in a slightly different part number.https://www.sparkfun.com/products/10079
RTD Thermistor Fine Tuning circuit - Page 1
Forum section: electronics / projects

author: Adam12
author_rank: Newbie
timestamp: July 27, 2015, 09:12:03 pm
content: Hi,I'm looking for help designing a circuit that can fine tune/calibrate the output of an RTD Thermistor. Looking for an accuracy of 0.1 ohms and a linear range of 0 to 10 ohms. I thought it would be as easy as a single POT but I can't seem to find the part with those specs.What's it for?I have 3 RTD thermistor temperature probes that feed one PID(MYPIN TA4 temperature process control module). I'm using rotary knobs to switch between probes and there is a 0-2 degrees fahrenheit temperature variance between the probes that I hope to null with this circuit. I'll duplicate this circuit and apply it to two of the RTD's to match the "master" RTD.Thanks for any help.Adam12

author: retrolefty
author_rank: Super Contributor
timestamp: July 27, 2015, 10:19:54 pm
content: QuoteA thermistor sensor is not an RTD sensor..QuoteRTD's are usually processed with a wheatstone bridge/instrumentation amp. Any 'matching' should probably be handled via firmware calibration function after performing the raw ADC conversions.

author: Adam12
author_rank: Newbie
timestamp: July 28, 2015, 04:19:07 am
content: retrolefty,Thanks for replying. Please forgive me. My background is in avionics and I've never worked in this area. My sensors (3 of them) are RTD Pt100 ohm Sensors. There is an offset temperature function on the PID to "calibrate" to a known temperature. The problem is that the PID is only made to support one sensor at a time. Me, being cheap am trying to do a workaround by putting a switch between the sensor and PID, to switch between the sensors and it works. But, there is about a 2 degree difference between sensors when measuring the same temperature. I was hoping I could put a trimmer circuit between two of the sensors to match the "primary" sensor. when figuring my tolerances measuring the resistance between the RTD's leads I calculate I need a 0.1 ohm tuning capability to really dial in the temperature.In my initial research into POTs I'm finding it's more difficult than I originally thought and think a series/parallel multiple POT circuit might do the trick. This is where my brain ceases to work.A basic concept is at the top left of the "signal flow" diagram.The actual switch pinout is at the bottom left of the other diagram. I'm using three separate thumbwheel switches to accomplish the switching.S1 S2 S3 and P1 P2 P3 are used interchangeably and there are two blue leads and one red lead per sensor. My plan was to place the trimmer pot on the red lead.Thanks!