hybridfree/eevblog-posts huggingface dataset:
Low-current, 60V from battery - Page 1
Forum section: electronics / projects

author: andrewj
author_rank: Newbie
timestamp: July 11, 2016, 02:44:51 am
content: What would be my best option for stepping up a battery source to 60V? The circuit would only draw about 50mA. I was thinking something like a single 9V or a couple of AAs. LiPo's might work too. I've looked at DC-DC step-up modules but these are pretty bulky and overkill for the application. They also have high input voltage requirements >8V. I picked one up from Amazon that makes an audible clicking noise probably because the load is so small. Any ideas?

author: Ian.M
author_rank: Super Contributor
timestamp: July 11, 2016, 03:49:42 am
content: 50mA load at 60V is 3W. Assuming 85% efficiency, that's 3.5W in. You can forget about the 9V battery or two Alkaline AAs because the output voltage will collapse at high load currents and you'll never get 3.5W out of them.Heavy duty LiPO/Li-ion or NiMH are an option, but higher voltages will make the design much easier as the input current will be reduced. I wouldn't want to design for less than 6V in e.g. 6 AA NiMH or two 18650 Li-ion or a 2 cell LiPO pack.If you have to use primary cells, 4 AA would be marginal, with a service life of about an hour so you, d do better to use 4 C cells or 8 AAs.Linear Technology's LT1170HV is a possibility but if you don't have prior experience of building switching power supplies, its not likely to go well.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 11, 2016, 05:19:34 am
content: A multi cell lipo pack adds balancing issues. One solution could be to use a pack with the balancing circuit built in, but you're probably going to have a hard time finding one of those smaller than a laptop battery. 3.5W isn't unreasonable for a single lithium cell large enough to get a decent runtime. Since the voltage ratio is relatively large, a flyback or tapped boost ("flyboost") topology would probably be your best bet.What's the end application? About the only ones I can think of would be a portable power supply for condenser microphones or a small tube (pre)amp.
Low current battery charging? - Page 1
Forum section: electronics / projects

author: XFabricate
author_rank: Newbie
timestamp: August 23, 2022, 08:02:50 pm
content: I had a question about battery charging if anyone could help. I'm looking at using a cheap usb charging board with a TP4056 on it but according to the datasheet it can only go down to 130mA as a minimum charge current. The battery I'm using meanwhile has a maximum charge current of 11mA. Can I put a resistor in series with the battery to reduce the current or would that interfere with the charger? Is there a better (cheap / easy) charger for this kind of application?Thanks!

author: Benta
author_rank: Super Contributor
timestamp: August 23, 2022, 08:32:19 pm
content: You have the wrong charger for that battery. Forget about fiddling with resistors etc.It would interest me which battery you have. That charging current makes makes think it's the size of a pinhead.

author: XFabricate
author_rank: Newbie
timestamp: August 23, 2022, 09:00:07 pm
content: Quote from: Benta on August 23, 2022, 08:32:19 pmI knew it was the wrong charger but I already have a bunch of them and wanted to see if I can make it work before looking for something else. It doesn't have to be perfect as it's just for a prototype test. I just need to get some charge into the battery a few times without it exploding.Your guess isnot far offfor the battery size.

author: Benta
author_rank: Super Contributor
timestamp: August 23, 2022, 09:59:17 pm
content: Wow! I'm flashed by that Li-cell.I don't see a ready-made IC anywhere.I think you'll have to make a 4.2 V, 5...10 mA, current limited charger yourself. You already have 5 V from the usb, the rest should be easy.

author: tunk
author_rank: Super Contributor
timestamp: August 23, 2022, 10:15:17 pm
content: Try with a Rprog=120k resistor and see if you get 10mA.The datasheet also says: Ibat=1200*Vprog/Rprog, Vprog=1V

author: Benta
author_rank: Super Contributor
timestamp: August 23, 2022, 10:24:06 pm
content: That datasheet is as lousy as most other chinese products. No information at all on the "PROG" pin input current.But try it out and come back with the results, please.Cheers.
Low current boost converter modules up to 110V at 1A? - Page 1
Forum section: electronics / projects

author: Chris56000
author_rank: Frequent Contributor
timestamp: September 21, 2018, 05:06:47 am
content: Hi!I'm thinking of building the Sussex Valve Tester on the Vintage Radio Forum, what I would like to add to it is a Step Up Boost Converter Module to test series–operated valves, where the heaters may be up to 70V, but not a large current – 500mA is adequate!Does anyone know of any cheap modules, either in kit form or built, that can give up to about 70–100V (max) at 500mA that can be varied down to about 15V?Ideally I want one mainly through–hole parts, and as cheap as possible – £15 max!There is a 12–80V one but it's quite big with a large heatsink, and I'm looking for a smaller sized one!I've asked in this Forum as the Members here have a much wider view of whats available, and also the Vintage Radio Forum bans ebay links – it is much more strictly moderated!Chris Williams
Low current lithium battery recharge and hold (float charge) - Page 1
Forum section: electronics / projects

author: AloyseTech
author_rank: Regular Contributor
timestamp: December 10, 2024, 03:44:00 pm
content: Hi,I have a lithium-ion powered device which can besometimesconnected to an external communication bus. A little bit of energy can be "harvested" from this bus, around 4mA at 5V. I'd like to use this available energy to maintain the lithium ion battery at roughly 50% of its charge. The battery is a protected (typical DW01-like circuit + PTC fuse) 700mAh cell. The device itself uses around 200uA on average with a few activity phases at around 200mA.I though about using a current limited voltage source (based on TL431), set to 4.1V 3mA, with a schottky diode in series (so around 3.8V) to the battery like this :https://tinyurl.com/25tarcvqI'm not sure about the behavior of the battery but I assume it could sink current even when it is charged in CV mode. And in this case current would flow continuously which is bad and could cause damage to the battery (not overcharging though, as it should not charge above the set voltage of 3.8V).Is it necessary to implement duty-cycled charging or some sort of very low current threshold detection to stop charging ?I understand that it's a complicated topic and and I could not find really factual evidence wether or not the idea is safe in general. So if anyone has some literatur about the topic that would also be awesome.ThanksRelated threads :https://www.eevblog.com/forum/projects/float-charge-voltage-for-liion-cells/https://www.eevblog.com/forum/chat/lipo-battery-on-holdingfloat-charge/https://www.eevblog.com/forum/chat/is-big-clive-right-about-lithium-battery-charging/https://www.eevblog.com/forum/projects/float-charging-lithium-ion-batteries-at-lower-voltages/https://www.eevblog.com/forum/projects/float-charging-li-battery-for-fluke-845ab-null-meter/https://www.eevblog.com/forum/projects/lithium-charging-ic-with-low-ground-pin-current/msg1185739/#msg1185739

author: AloyseTech
author_rank: Regular Contributor
timestamp: December 12, 2024, 05:52:45 pm
content: I found that Analog Device sells a shunt based battery charger for energy harvesting application : LTC4070 and LTC4071. According to the datasheet (https://www.analog.com/media/en/technical-documentation/data-sheets/LTC4070.pdf):QuoteUnfortunately they don't provide much more information.
Low current switch control high current circuit? - Page 1
Forum section: electronics / projects

author: hal9001
author_rank: Regular Contributor
timestamp: March 24, 2021, 11:17:25 am
content: Is it possible to have a low current rated switch (50 mA) turn a high power (1 A) circuit completely on and off without any leakage current? The circuit can be powered with batteries and I don't want current use when the circuit is off. I have an idea of connecting the switch tothe gate of a MOSFET thats in series with the input supply but suspect there will be leakage current this way.

author: mhuber1
author_rank: Newbie
timestamp: March 24, 2021, 01:29:58 pm
content: the answer is simple just use a small relay

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 24, 2021, 01:34:21 pm
content: Quote from: hal9001 on March 24, 2021, 11:17:25 amIt would be negligible compared to the self discharge of a battery capable of supplying 1A.

author: ajb
author_rank: Super Contributor
timestamp: March 24, 2021, 03:33:17 pm
content: If the only concern is the power consumption and you don't otherwise NEED a mechanical switch, a MOSFET should be fine. Gate-Source leakage and Drain-Source leakage will be specified in the datasheet, and are typically in the microamps even for chunky parts designed for high power switching.If for some reason a solid state switch won't work, latching relays exist. They need only a ~few millisecond pulse of power to switch, and no coil current is required to maintain their position. The have the downside of being slightly more complicated to drive (need at least one additional transistor depending on coil configuration, possibly extra capacitors to supply the pulse energy) and not necessarily being suited to high acceleration environments which can potentially dislodge the latched contacts, but you can't beat them for steady state power consumption when you need a mechanical switch.That said, depending on duty cycle and switching rate the average power consumption of a latching relay is probably higher than that of even the leakiest (within reason) MOSFET you'd use.

author: wizard69
author_rank: Super Contributor
timestamp: March 24, 2021, 05:53:25 pm
content: How the circuit is used is a big factor here. A relay is a positive way to interrupt power and you are not likely to get leakage. However a relay uses power and frankly in some applications it can be considerable. A FET might have only modest leakage but you would need to model that over time to see how much energy you would lose vs running a relay when on.As others have noted you can get latching relays that can greatly impact energy loss during on periods. You would still need to know your switching Frequency to determine if the energy loss would be less or more than a FET.Quote from: hal9001 on March 24, 2021, 11:17:25 am
Low current white LED - Page 1
Forum section: electronics / projects

author: wigman27
author_rank: Regular Contributor
timestamp: October 31, 2013, 11:02:28 pm
content: Hey all :-)I am working in a project for a mate, he wants to install a white LED inside a 3mm diameter tube to shine through some little bead type things. Apparently they have really small images inside them.The size isn't the issue, the problem is he has to use a 3mm diameter battery, which there aren't many of.. One he has found is a lithium cell used in floats, it's a 20mah battery at 2.5 - 3v. The recommended current draw is 500 micro amps.Does anyone know of an LED that will work well enough at that lower current with a Vf of around 2.5v?I have found a few but not sure how well they will work that low down.Thanks :-)

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 31, 2013, 11:07:02 pm
content: The most efficient LEDs will be white, with high colour temperature.You will probably need to boost the voltage - you may get a little output at 2.5V, but not much

author: wigman27
author_rank: Regular Contributor
timestamp: November 01, 2013, 12:00:16 am
content: Yeah I thought that may be the case, I don't thing I will be able to fit a boost circuit on board so I may need to try and get some shorter batteries and put 2 in series. He is pretty keen to put the shortest amount of tubing possible.

author: IanB
author_rank: Super Contributor
timestamp: November 01, 2013, 12:06:26 am
content: From time to time I have obtained various novelties about the size of a small tie clip or badge with a flashing red LED in them. They use a miniature button cell and a very tiny boost/flash circuit. Red LEDs of course have a low enough Vf to run from a 3 V lithium cell and the flashing circuit dramatically reduces the current consumption.So something like that might be a possibility? Does it have to be white?
low current/voltage magnetic power connector - Page 1
Forum section: electronics / projects

author: ballen
author_rank: Regular Contributor
timestamp: December 31, 2022, 08:00:53 am
content: I need to provide power (4.2V at max 150mA) via a cable to an optical device. I'd like to arrange things so that if the cable is yanked, the cable "break free" so that the optical device is not pulled onto the floor. What I have in mind is something like Apple's "Magsafe" connectors, but ideally a bit smaller and better designed.A search at Mouser turned up Mill-max magnetic (pogo pin) connectors, at Digikey I didn't find anything. I don't like the Mill-max design very much. It seems overkill for my current/voltage requirements, and is bulkier than I would like. I was wondering, are there other options?

author: Terry Bites
author_rank: Super Contributor
timestamp: December 31, 2022, 01:22:19 pm
content: As most connectors are a designed not to fall out, you're going to be up against it.I searched for "pull away connector" On google.I found these USB C typeswww.aliexpress.com/w/wholesale-USB%20C%20Magnetic%20Adapter.html?isseo=y&seosc=googlesearchboxOn amazon as wellAnd I saw thishttps://www.aliexpress.com/item/1005001573396293.html?spm=a2g0o.productlist.main.19.6f7a1206SXLOxT&algo_pvid=be907310-4818-4540-8eae-701dbe5805a4&algo_exp_id=be907310-4818-4540-8eae-701dbe5805a4-9&pdp_ext_f=%7B%22sku_id%22%3A%2212000016639428115%22%7D&pdp_npi=2%40dis%21GBP%211.34%210.94%21%21%21%21%21%402100b5dc16724924547143599d073e%2112000016639428115%21sea&curPageLogUid=SuuzVMEDUhrsPractically giving them away!I had a problem with people walking off with kit before unplugging it.So I put on a steel wire lanyard that was shorter than the power lead.They had to unloop from a wall hook it or overcome 25Kg of yank. That baffled them!

author: SeanB
author_rank: Super Contributor
timestamp: December 31, 2022, 01:52:44 pm
content: You do get USB cables with a magnetic end, so they might be useful. Just have to have a USB micro end on the one side, and then it will magnetically lock together.Edit to add generic Amazon link as example.https://www.amazon.com/Charging-Magnetic-Micro-USB-Cable/s?k=Charging+Magnetic+Micro+USB+Cable
low density esd foam - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 11, 2019, 03:52:45 am
content: HiI just bought some ESD foam mats for DIP ICs, or so I thought.https://www.ebay.ca/itm/3-5-10mm-ESD-Anti-Static-High-Density-Foam-Antistatic-Insertion-200x200mm-Black/282886584062?ssPageName=STRK%3AMEBIDX%3AIT&var=582415070630&_trksid=p2057872.m2749.l2649The stuff is way too dense, the pins bend before the chip goes in. I am used to foam that has larger bubbles and is crumbly, chips go in with very little force.What terms should I look for?(Why yes, I had so much of the good stuff that it lasted me decades. Now it's actually decaying so I need more and forgot what to look for)

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 11, 2019, 06:13:00 am
content: You want 'open cell' or 'low density' ESD foam.I see some there on ebay, and as is usually the case, some stuff that is called high density has pictures of the open cell low density stuff.You might have to go by the pictures to get what you want.

author: Mr. Scram
author_rank: Super Contributor
timestamp: January 11, 2019, 06:36:03 am
content: I think I bought some of that harder stuff a while back. I've never been sure it's actually any kind of ESD foam. It smells and feels like any other regular foam and I unfortunately don't have the kit to test it properly.
Low distortion, wideband IQ modulator - Page 1
Forum section: electronics / projects

author: ezalys
author_rank: Frequent Contributor
timestamp: September 07, 2021, 04:42:18 pm
content: Suppose I have a wideband sinusoid coming in between 100 Hz and 1 MHz. I want to precisely IQ modulate this signal with analog control and wind up with a signal that, again, is a high quality sinusoid. I would like to have less than 0.5 degree of phase error if possible. Any suggestions that don't involve DSP? I'm asking this out of my own edification, since I do already have a DSP solution in mind, I'm just curious if there's a good analog solution.

author: ezalys
author_rank: Frequent Contributor
timestamp: September 07, 2021, 04:58:46 pm
content: Actually -- let me throw out an idea to just get things going.We suppose a high quality sinusoidal 50 MHz source which goes through a 90 degree phase shifter. This shift can be precise since it's narrow-band.These 50 MHz I and Q signals go through a sampling mixer (sampling mixer is key to get high quality downconverted signal), both driven by the same 50-51 MHz square wave VCO. VCO is servoed to get I mixer output to phase match the incoming sinusoid.Finally, downconverted I and Q go through leveling loops and then four quadrant multipliers, and then summed. Not sure which four quadrant multipliers will have sufficient leakage performance at 1 MHz to hit my phase error target, but it's an idea. Would likely rip off as much as possible from the 4192A impedance analyzer as possible, where modern integrated solutions are unavailable.

author: David Hess
author_rank: Super Contributor
timestamp: September 07, 2021, 07:09:17 pm
content: Are available analog transconductance multipliers not good enough? They might have to be trimmed but see below about CMOS switches.Can't the 90 degree phase shift be generated with simple logic? I have seen it done this way before. An old National Semiconductor application note discusses using CMOS switches for IQ modulation/demodulation but at lower frequencies.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: September 07, 2021, 09:06:15 pm
content: common practice, like for the SoftRock radio include a 74AC74 for the I/Q phase shift, while for the mixer some use common 74HC4066; also 74HC4052 can be seen, though I made better experience with the FST3253
Low dropout linear voltage regulators - Page 1
Forum section: electronics / projects

author: grifftech
author_rank: Frequent Contributor
timestamp: March 21, 2017, 08:54:04 pm
content: Why is the pinout different compared to regular voltage regulators, and is the 15 volt max voltage input to ground?ldo:http://www.st.com/content/ccc/resource/technical/document/datasheet/99/3b/7d/91/91/51/4b/be/CD00000544.pdf/files/CD00000544.pdf/jcr:content/translations/en.CD00000544.pdfregularhttps://www.fairchildsemi.com/datasheets/LM/LM7805.pdf

author: Kleinstein
author_rank: Super Contributor
timestamp: March 21, 2017, 09:01:26 pm
content: The pin-out with TO220 and similar parts depends one which pins is connected to the substrate. This is usually the one in the center to give the best heat flow. This is why essentially all transistors / MOSFETs in TO220 have the collector / source in the center.

author: grifftech
author_rank: Frequent Contributor
timestamp: March 21, 2017, 09:06:21 pm
content: Quote from: Kleinstein on March 21, 2017, 09:01:26 pmthis is NOT a MOSFET.

author: Benta
author_rank: Super Contributor
timestamp: March 21, 2017, 09:13:56 pm
content: Plenty of LDOs with normal pinouts around. LM2940, for instance.
Low EMI 802.3bt PoE GbE PSE (Power supply) - Page 1
Forum section: electronics / projects

author: larry42
author_rank: Regular Contributor
timestamp: February 15, 2021, 02:48:32 pm
content: Hi! Anyone have tips for the best (w.r.t. lowest EMI) 60W+ (IEEE 802.3bt) PoE supply that is capable of Gigabit data for an industrial project.Input power ideally 230Vac, metal shielding if possible for RJ-45 shield termination.Edit: I want to buy off the shelf - no time to design one (and way too expensive w.r.t design time / testing / production qty).

author: KT88
author_rank: Frequent Contributor
timestamp: February 15, 2021, 09:32:19 pm
content: I guess you are looking for the PSE side of POE...Here is a good starting point that I'm aware of:https://www.analog.com/en/search.html?q=IEEE%20802.3btCheersAndreas

author: larry42
author_rank: Regular Contributor
timestamp: February 16, 2021, 06:48:34 am
content: Thanks - but I want tobuyCOTS, not build (I'm already designing the rest of the system - no time for yet another design)
Low frequency oscillation from op-amp when driving large inductive load - Page 1
Forum section: electronics / projects

author: tom66
author_rank: Super Contributor
timestamp: December 03, 2012, 12:43:14 am
content: I am designing a little project which will impress a high frequency (1kHz) sine wave through a battery at a set and precise (±0.5%) current amplitude. This wave must be impressed on a constant DC current load which could be of either polarity (charging or discharging.) The current is then picked off and converted to DC using an RMS-to-DC IC which lets us measure the real-time ESR of the battery while it is charging or discharging.In order to do this I decided to use a 2:1 coupling transformer and capacitor because it allows me to easily measure the current with a single resistor and use an op-amp in a non-inverting configuration.This works, but (not entirely to my surprise), there's quite a bit of instability at the start in LTspice. I'm a little worried the circuit may be unstable completely when built for real. The oscillation appears to reverse when the op-amp begins clipping (current limiting) -- but I worry it could sustain itself indefinitely if the clipping is a little softer like it might be on a real op-amp. Is there an easy way to make the circuit "unconditionally" stable? I found I could make it more stable with a series resistor in the primary -- and in the secondary -- but it doesn't fully stabilise even with a large resistor, and of course a really large one limits the current too much. I also added a small feedforward capacitor, but I'm not at all sure how to calculate its value.Because the transformer very effectively filters out low frequency, none of the oscillation appears on the output, except for a little clipping right at the start. So, apart from this worry, the circuit -should- work.Edit: Clarification - R5 represents the op-amp output current. This is the unstable part that has me worried.Excuse my lack of op-amp knowledge...

author: free_electron
author_rank: Super Contributor
timestamp: December 03, 2012, 04:29:05 am
content: Build it and try. Modeling transformers is difficult in spice... Especially the behavior of the core material and things like core saturation.

author: GK
author_rank: Super Contributor
timestamp: December 03, 2012, 05:41:14 am
content: Putting the transformer into the op-amps global feedback loop isn't a good idea at all. You don't need a transformer anyway. GoogleHowland current pump.
Low Leakage Capacitor for DS3231 RTC - Page 1
Forum section: electronics / projects

author: scott216
author_rank: Regular Contributor
timestamp: November 02, 2014, 11:47:21 pm
content: The data sheet for theMaxim DS3231 Real Time Clocksays to use a low leakage decoupling capacitor between 0.1 to 1.0uF. I don't know much about low leakage caps, but I read film capacitors are pretty low leakage, so I chose this one from Digikey:http://www.digikey.com/product-detail/en/ECP-U1C224MA5/PCF1128CT-ND/285455Is this a good choice?

author: gxti
author_rank: Frequent Contributor
timestamp: November 03, 2014, 12:02:56 am
content: An ordinary 100nF ceramic capacitor would be fine, as they have negligible leakage.The datasheet says says "low leakage" because the RTC draws so little current that you can run it from a lithium coin cell or supercap for a very long time (months to years). If you have a leaky electrolytic cap across the supply rails though it will shorten the battery life considerably. If you are not intending to run the RTC off a small battery for a long time then the "low leakage" spec is irrelevant.

author: scott216
author_rank: Regular Contributor
timestamp: November 03, 2014, 12:34:44 am
content: I figured that was the reason. It's for an alarm clock that I'm giving a friend, so most of the time it will be plugged in, but it could also be the case they stop using it for a while and unplug it.

author: TarHeelTom
author_rank: Newbie
timestamp: November 03, 2014, 04:49:41 am
content: Don't know if they're still around, but ran into a 0.1 farad 5 volt tantalum capacitor at Radio Shack many years ago and bought it just for grins.Charged it to 5 volts and put it back in the blister pack and threw it in my dresser drawer.For about 5 years or more I pulled it out once a year and put it to a cheap voltmeter. Last time i tested it, it still read 5 volts.I need to dig through my dresser and see if I've still got that thing. Curious to see what it's got for voltage now.Tom

author: SeanB
author_rank: Super Contributor
timestamp: November 03, 2014, 06:17:15 pm
content: Use a 0.1F 5V5 supercap, it will hold the clock running for a month if the external battery was disconnected.

author: scott216
author_rank: Regular Contributor
timestamp: November 03, 2014, 10:03:40 pm
content: Quote from: SeanB on November 03, 2014, 06:17:15 pmThat's a good idea. Would the supercap also take care of decoupling, or would i still need a different cap to do that?

author: dannyf
author_rank: Super Contributor
timestamp: November 03, 2014, 10:24:54 pm
content: :That's a good idea. :read more about super caps and their limitations before you commit to it.
Low logic switching question - Page 1
Forum section: electronics / projects

author: Electron_1
author_rank: Contributor
timestamp: March 31, 2015, 07:51:59 pm
content: Hi guys,Just wondering if somebody could point me in a good direction. I am making an opto-isolated breakout board for the limit switches on my CNC machine and am breadboarding it at the moment.When I trip the limit switch the logic (3.3v) goes low. I have a separate 5v supply on the board which is powering an LED. I was wondering what the simplest way to activate this circuit might be ?Basically what I'm trying to achieve is that when my 3.3v goes to 0v my 5v circuit switches on and lights a warning LED and when my 3.3v is at 3.3v my 5v is off. I could use an IC but I presume there is an easier way ?Many Thanks.

author: moffy
author_rank: Super Contributor
timestamp: March 31, 2015, 11:00:49 pm
content: You could use an NPN transistor e.g. BC547, connect the emitter to ground a 1k resistor to base as input(from 3.3v logic), and a 1k connected between collector and +5v. It will give a low output when the input is HIGH and a +5v output when the input is LOW.

author: Electron_1
author_rank: Contributor
timestamp: April 01, 2015, 07:02:40 pm
content: Hi. Thanks for your answer.I've just been playing around with this configuration on a breadboard and have some problems.The only transistor I have here is a ULN2803 darlington array. In theory everything works out fine. I connected everything as suggested and when I trip my limit switch my 3.3v logic goes low and my 5v goes high activating the LED and also informing the CNC software that a switch has been triggered and to kill all activity. However when I deactivate my limit switch (it's an inductor switch) my 5v goes low and my 3.3v goes high. However it only goes to 1.7v instead of 3.3v. Unfortunately this is not enough for the software and so it thinks the switch is still triggered. I presume I'm dealing with a voltage drop across the ULN2008 and am wondering how to combat this ? I'd really like to make it work with this chip if possible, as it's quite difficult to get parts where I live and can sometime take me weeks to access new components.Again any help is appreciated.

author: Electron_1
author_rank: Contributor
timestamp: April 03, 2015, 06:41:16 pm
content: Hi guys,Would love if someone could guide me. I'm having a hard time trying to figure out where I'm going wrong.Have used the method moffy described above (thank you moffy) but I can't really get my head around whats happening.I've tried this with both a ULN2803 and a 2N3904BU. My 3.3v logic is coming from the output of a 4N25 opto-isolator.I've fed this through a 1k resistor to base, my emitter to ground and my + 5v through a 1k resistor to the collector. Both chips are exhibiting similar characteristics.Basically my 3.3v is returning to around 1.7v in the case of the ULN2803 and about 1.5v in the case of the 2N3904BU.This means that my software cannot deactivate the limits as it is not reading 3.3v.I'm sure I'm doing something simple incorrectly ?
"Low noise" 5V linear PSU - Page 1
Forum section: electronics / projects

author: UpLateGeek
author_rank: Contributor
timestamp: May 18, 2018, 11:47:20 am
content: Just looking for some suggestions/advice on designing a low noise linear power supply for a DAC that's powered by 5V USB. I've only ever worked with digital stuff, so I have no idea if my bypassing is good enough or overkill, or if there's any basic analogue circuit design tricks I should know.Also, I'm guessing the shield should be grounded (the metal case of the DAC is connected to the shield of the USB power connector, coax input and analogue outputs), but should that ground connect to the 0V rail? And if so, should I just use a ground plane, or is it worth it to use a star ground?Here's my design:Any comments would be appreciated!

author: Zero999
author_rank: Super Contributor
timestamp: May 18, 2018, 12:35:07 pm
content: The ripple rejection can be improved, by putting a fairly large capacitor across R2, say 10µF to 100µF.Why is R1 a potentiometer? For fixed power supplies, it's better to just use the right resistor values. R1 = 1k5 and R2 = 4k3 will get 4.988V, which is within 0.24% and better than the NJM2397's tolerance. Even if you manage to adjust it to better than this, the voltage can still change by more than this due to the line and load regulation. If you're a volt nut than you could use E96 values: R1= 1k21 and R2 = 3k48, but it's overkill.

author: UpLateGeek
author_rank: Contributor
timestamp: May 18, 2018, 01:07:19 pm
content: Quote from: Hero999 on May 18, 2018, 12:35:07 pmFine, I'll go buy some more resistors.But thanks, both good suggestions.
Low-Noise Buck For Bias Supply - Page 1
Forum section: electronics / projects

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: August 21, 2020, 12:48:05 am
content: I'm struggling a bit identifying appropriate buck. Here's the requirements:VIN=10-40V, nominal 24VVOUT = 1.8VIOUT = 20mA max, 5mA nominalI've currently got this implemented with TPS54061, but the problem is that I originally designed for the full 200mA capability of the part in DCM, but under real load conditions (much lower, more like 5mA), I get pulse-skipping. This is creating noise in band of interest (10-40kHz) that is coupling into sensitive signal conditioning circuitry. Using TPS54061 design spreadsheet, I can't solve for DCM solution at this light load and avoid pulse skipping. There seems to be solution for CCM, but then again, TPS54061 doesn't have all that low IQ to begin with.Does anyone have any suggestions for a high conversion ratio buck, low output current, that isn't going to generate all sorts of skip/pulse/ECO mode noise in the 10-40kHz region?

author: pardo-bsso
author_rank: Frequent Contributor
timestamp: August 21, 2020, 01:26:36 am
content: I presume that going linear or adding a stable minimum load is not suitable for your application?

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: August 21, 2020, 11:47:26 am
content: Quote from: pardo-bsso on August 21, 2020, 01:26:36 amLinear, no, since that increases power by an order of magnitude. Minimum load, possibly. I am going to take a stab to get TPS54061 designed into CCM mode first and see if that resolves the problem.

author: KT88
author_rank: Frequent Contributor
timestamp: August 21, 2020, 12:27:22 pm
content: The ADP2360 could fithttps://www.analog.com/en/products/adp2360.htmlIt uses PFM which could create issues as well but in a quick sim I got >90kHz out of it at 40V/5mA.

author: David Hess
author_rank: Super Contributor
timestamp: August 22, 2020, 04:36:58 pm
content: The problem is that the TPS54061 implements fixed current sensing internally so operating at low current is prone to noise. A part with external current sensing could be adjusted to operate properly or a voltage mode controller could be used. A higher output inductance will ensure CCM operation at low current.A tapped output inductor could be used to raise the peak current and duty cycle but that requires external power switches and an expensive inductor.

author: Evan.Cornell
author_rank: Regular Contributor
timestamp: August 22, 2020, 10:28:25 pm
content: Quote from: David Hess on August 22, 2020, 04:36:58 pmThe internal sensing is the problem.. I tried modifying the circuit for much higher L, was still getting the noise. See TI e2e post with more details here:https://e2e.ti.com/support/power-management/f/196/p/933931/3450237TI recommended changing to one of their parts with forced PWM (FPWM) mode, which is the path I will take.
Low Noise Coax, Low Triboelectric Noise  - Page 1
Forum section: electronics / projects

author: LaserSteve
author_rank: Super Contributor
timestamp: October 16, 2020, 07:00:42 pm
content: Anybody know where I can get RG-58 in low noise cable by the foot?Application is measurement of charge on a very small capacitor (10s of pf) with a moving charged electret dielectric. Cap is air spaced and in a research lab.I need BNC to capacitor. I'm aware of the Keithley cable but the price is beyond what we can afford right now.Cable needs to be reasonably flexible but is fixed in position during the measurement.So, Low noise, solid dielectric, high braid percentage, and braid bonded to outer insulation, braided inner conductor, I believe is a start. Please correct me if I am wrong.Steve

author: TimFox
author_rank: Super Contributor
timestamp: October 16, 2020, 09:35:43 pm
content: The good low-noise coax has a conductive layer in intimate contact with the dielectric outer diameter, such as Belden 9239 (approximately the same size as RG-174, with 44 pF/foot capacitance). Traditionally, this was graphite, but this Belden cable uses a thin conductive plastic (PVC) layer outside of the solid polyethylene dielectric. According to the manufacturer's websitehttps://catalog.belden.com/techdata/EN/9239_techdata.pdfit is available in 100 foot lots, which is probably more than you need.

author: branadic
author_rank: Super Contributor
timestamp: October 16, 2020, 09:53:24 pm
content: www.koax24.dehas some nice overview of possible low noise cables:Coax:https://www.koax24.de/produktinfos/koaxialkabel/koaxialkabel-50-ohm.htmlTriax:https://www.koax24.de/produktinfos/triaxialkabel/uebersicht.html-branadic-

author: sdouble
author_rank: Frequent Contributor
timestamp: October 18, 2020, 08:15:56 pm
content: lmr195 ?RG58 compatible connectors.pretty good shieldingfoamed PE dielectric though.

author: tggzzz
author_rank: Super Contributor
timestamp: October 18, 2020, 09:30:02 pm
content: Could you put some of the electronics right next to the capacitor, and transmit the information using standard coax?

author: graybeard
author_rank: Frequent Contributor
timestamp: October 18, 2020, 10:07:04 pm
content: Why not use triax with a driven shield? The driven shield makes the effective capacitance from the center conductor to it effectively zero. That is why electrtometers and almost all semiconductor test equipment use driven shield triax.All you need is a voltage follower to drive the shield. For low 10s of pF you can probably get away without using triax connector at the end if the connections are short.
low noise PIC MCU? - Page 1
Forum section: electronics / projects

author: CopperCone
author_rank: Super Contributor
timestamp: January 21, 2018, 01:22:12 am
content: http://www.microchip.com/design-centers/emcThey have some before and after spectrums.do you think a PIC18F4685 falls into the before or after? What similar PIC can I choose that has the "after" specification?Does it go by manufacturing date? Or product line?

author: Kleinstein
author_rank: Super Contributor
timestamp: January 21, 2018, 09:04:08 am
content: How a chip is made can have quite an effect on EMI. So a µC that produces less RF emissions is a good idea to make it easier to meet the EMC requirements. You should still use a good layout, but could get away with a few saved caps or without the choke. Eve if this only helps to pass the EMC test more often on the first attempt, it helps.An example for a chip that is not very EMI friendly is the old NE555 - during switching it produces quite some cross conduction current pulse on the supply and this way can cause quite some trouble. In this case it's not so much EMC relevant emissions, but interference with other parts of the circuit. Also the case / pinout can be a factor: The old way of having the supply pins at the far ends of a DIP40 is kind of a bad idea - so newer chips changed that to supply ad adjacent pins in the middle.With the PICs this might be more like a problem with some older PICs that produce a relatively high amount of emission - using CMOS that can run over a relatively large supply range is kind of pointing that way. So it could be as well a poor older PIC.

author: Andreas
author_rank: Super Contributor
timestamp: January 21, 2018, 10:28:23 am
content: Quote from: CopperCone on January 21, 2018, 01:22:12 amBefore: typical emissions by your design before you have visited their EMC-seminarafter: that what you can reach after having visited the seminar.best regardsAndreas

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: January 21, 2018, 01:11:35 pm
content: I don't know if you are aware but a lot of latest PIC18s have output buffers slew rate control and the default power-up setting is reduced slew rate.This will magically reduce EMI for those who have no idea.It will also stop an older high performance design working if you just drop the new chip in. Luckily it's just a register setting and it's good to have a choice.Leo

author: CopperCone
author_rank: Super Contributor
timestamp: January 22, 2018, 05:56:26 pm
content: Even if you use filters its still better if the noise is not there in the first place. It says it was measured in a tem cell. You would need to surrround the chip with filters to prevent this noise. I am doing sensitive analog work so the lilly will be gilded anyway, i dont see it different then choosing a low noise opamp.

author: chris_leyson
author_rank: Super Contributor
timestamp: January 22, 2018, 06:43:53 pm
content: Given that the PIC18F4685 is an older generation 5V part and a lot of the newer generation 3.3V parts like PIC24 and DSPIC run the core at 2.5V and the fact that the PIC18F4685 has 25mA pin drive capability I would say it falls into the before catagory.
Low noise, portable +/- 12V PSU - Page 1
Forum section: electronics / projects

author: moffy
author_rank: Super Contributor
timestamp: May 08, 2019, 12:28:02 am
content: I was trying to do some noise/distortion measurements on an audio VCA I had made but I was getting 50Hz noise from my power supply. I was looking for around 100/110db of resolution for my measurement system. Even if I moved the wires a little the 50Hz noise would fluctuate, obviously induced pickup. So I went for a simple, cheap solution. Bought 2, 12V/2.4AH gel batteries from Jaycar and some terminals, and voila, a low noise power supply which is portable and completely isolated, so no ground loops.Testing went very well, unfortunately my VCA had around -80db of signal distortion. But the test setup, a Steinberg UR44 external sound card and my laptop had around 110db S/N ratio with the battery supply. For charging I already had one of those PRO type chargers that do multiple chemistries.Perhaps others might share any mildly unusual battery supply stories, I'm sure they would be interesting.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 08, 2019, 01:34:44 am
content: Were those really cheaper than using NiMH AA batteries?

author: moffy
author_rank: Super Contributor
timestamp: May 08, 2019, 01:37:31 am
content: Yes, especially from Jaycar. Simpler too, just cable tied them together no battery holders.

author: David Hess
author_rank: Super Contributor
timestamp: May 08, 2019, 03:06:33 am
content: I have used stacks of AA NiCd cells in the past to do the same thing. Batteries make fine low noise floating power supplies.

author: Gyro
author_rank: Super Contributor
timestamp: May 08, 2019, 09:07:37 am
content: You'd be well advised to add a couple of in-line fuses, otherwise it's only a matter of time before the insulation drips from your wires and the tracks lift off your PCBs.It won't hurt the noise performance.This style is compact and easy to find...https://www.ebay.co.uk/itm/5x-Inline-Standard-Blade-Fuse-Holder-Splash-Proof-DC-12V-30A-Fuses-For-Car-Bike/132727931095

author: mariush
author_rank: Super Contributor
timestamp: May 08, 2019, 09:30:03 am
content: Seems like it would have been easier to use 4 x 9v batteries for +/- 11v..20v, followed by two linear regulators.But i'm not aware of the power consumption.Could have used 24 AA or AAA batteries, rechargeable batteries and battery holders are cheap.

author: moffy
author_rank: Super Contributor
timestamp: May 10, 2019, 05:58:29 am
content: 2 by Pb-Gel in Oz are much cheaper and easier than 24 AA or AAA and remeber it has 2.4AH capacity. Yes the fuses are a very good idea, and I'll probably regret not putting them in somewhere down the line but I've gone minimalist i.e. Once I got something working I stopped(lazyness). One could put a set of regulators after the batteries for a variable supply.Quote from: David Hess on May 08, 2019, 03:06:33 amYes, they do work very well.
Low noise power supply design for OCXO - Page 1
Forum section: electronics / projects

author: smashedProton
author_rank: Frequent Contributor
timestamp: August 10, 2025, 03:45:00 am
content: kjl

author: radiolistener
author_rank: Super Contributor
timestamp: August 10, 2025, 10:27:16 am
content: Low noise power supply for OCXO - sounds serious! Though your post is so quiet, it’s practically noise-free already
Low operating voltage inductive sensor (or other industrial distance sensor) - Page 1
Forum section: electronics / projects

author: atwoz
author_rank: Regular Contributor
timestamp: September 05, 2013, 04:30:35 pm
content: Hello everyone,Does anyone know of a low operating voltage industrial inductive sensor? I need to detect a metal that will be 8mm away from the sensor. I need the sensor to be driven by a battery, so it will have to be turned on and off to conserve power. Also, it doesn't have to bee inductive, it can also be optical, but the requirement is to be able to drive the sensor with as little as 3v.What do you guys say? Am I asking too much, should I build my own sensor?Thanks.

author: cosmos
author_rank: Regular Contributor
timestamp: September 05, 2013, 04:42:55 pm
content: Internally these can often have circuit elements that work at low voltages...see the TCA505 for example.http://www.infineon.com/cms/en/product/power-management-ics/ac/dc/function-and-industrial-ics/ics-for-inductive-proximity-switches/channel.html?channel=ff80808112ab681d0112ab6a92d9056eIf you pulse operate them to reduce power be aware that they might not be as fast or as accurate at detecting objects as when they are not pulsed.

author: fcb
author_rank: Super Contributor
timestamp: September 05, 2013, 05:28:52 pm
content: 1. build a boost converter to generate the 24v (if you really need this).2. use a microswitch (okay okay I know)

author: atwoz
author_rank: Regular Contributor
timestamp: September 06, 2013, 03:47:36 pm
content: Thanks for the replies!I'm considering a boost converter, it should be more reliable that making my own sensor with one of those IC's..The idea would be to switch on and off the sensor by turning on and off the boost converter. I just don't know how much times a sensor needs to start working.Does anyone know of a boost converter that starts up pretty fast? I was looking at this onehttp://www.ti.com/lit/ds/slvs413e/slvs413e.pdfIt seems like it could work but looking at the startup graph (14) I count 1ms until the voltage stabilises, add to that the time the sensor needs to give correct readings.What do you guys think?

author: Impersonator
author_rank: Newbie
timestamp: October 12, 2015, 04:39:33 pm
content: Hey!I have the same screen, at least from a similar multi-machine-printer-thing, and i just tested with a 12v battery pack.The backlight of the LCD-screen lit up.Mark: I tested only on the back side of the screen, not on the pins 1-11.
Low or Zero force connector for 3d printer quick change head. - Page 1
Forum section: electronics / projects

author: FrankT
author_rank: Regular Contributor
timestamp: August 25, 2021, 11:39:01 pm
content: I'm looking at quick change tool heads for 3d printers.This can either be mechanical only, like the E3D offering, where each tool head has a full set of wiring or mechanical and electrical, like XChange by printermods.Does anyone know what type of connector the XChange uses (shown in the kickstarter videohttps://www.kickstarter.com/projects/printermods/xchange-v10-hot-swap-tool-changing-for-every-3d-printerat about 20s)? They are connecting to a pcb using that connector. How reliable, and what kind of life would that have, given it is for 3d printer hotend, so 24v 2-4A heater, 1-2A stepper, and signals.Are there any other inexpensive options? I have seen DIY solutions using pogo pins.Thanks,Frank

author: FrankT
author_rank: Regular Contributor
timestamp: August 27, 2021, 09:30:06 pm
content: To answer my own question, these seem to go by the name "Battery Connectors", or "compression connectors" although compression connectors finds many other types of compression connectors and compression fittings.Mill-max also has large range of pogo style pins, as well as multi-pin plug/socket assemblies.

author: thm_w
author_rank: Super Contributor
timestamp: August 28, 2021, 01:08:10 am
content: Yeah that looks like a custom made battery connector, but you could make your own with millmax pins.24V is a good choice, those contacts will be fine for 1A stepper. For the heater I would double them up.It looks like the kickstarter has 15 contacts total, so typical use might be:- 4 for stepper phases- 2 or 4 for heater- 2 or 3 for hotend fan + part cool fan- 2 for bltouch/z sensor- 2 spares (LED, NTC thermistor)https://www.aliexpress.com/item/32803931987.htmlhttps://www.aliexpress.com/item/1005002502275623.htmlhttps://www.aliexpress.com/item/4000128539681.html

author: RoGeorge
author_rank: Super Contributor
timestamp: August 28, 2021, 03:23:28 am
content: Those at sec 20 seems to be battery connectors. Usually made from a springy bent pin to be pressed against a flat surface.Some pogo-pins in parallel might work too. Pogo pins are telescopic cylinders with little springs inside, they are available in many sizes, some have rounded heads good to be pressed against flat surface.

author: FrankT
author_rank: Regular Contributor
timestamp: August 28, 2021, 10:23:19 pm
content: After a bit more searching, the exact parts are the Samtec SIR1 series. 2.6A per pin. 5000 cycles.3090 grams holding force per pin.Interestingly, the mill-max pogo connectors require 60g for 2A pins (or 120g for 10A pins), but are rated up to 1,000,000 cycles. 20 pins at 60g is 1.2kg contact force.EDIT: Correction the samtecs appear to require 90g per pin (I can't find it documented, but that's what is stated in the test results document)