hybridfree/eevblog-posts huggingface dataset:
DC Dummy load analog I OUT voltage conversion (Itech IT8500+ series) - Page 1
Forum section: electronics / beginners

author: lukasz.kostka
author_rank: Contributor
timestamp: May 15, 2021, 12:43:11 am
content: HiI've bought a ITech IT8511A+ DC dummy load. It has a BNC I OUT connector which outputs 10V/30A. All works fine on that output, problem is that ratio 3:1 is a odd value. My scope Rigol DS1054Z doesn't have any probe setting to scale it to a reasonable value. I've tried math as well but no luck. I've added a resistor divider to output with 3:1 ratio and all seems to work. Adding 2k, 1k results in too big load and signal is distorted. 20k, 10k is better. I think I will go with 200k, 100k 0.1% precision resistors.My question to you guys is this a valid good approach ? Seems simple to me. I did consider using a opamp but no way of powering it and requires a fast opamp with some external power supply.What do you think ?

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 15, 2021, 02:24:22 am
content: Without reading a device Technical Manual I can guess that a >10k load and <100k has to be fine.100k and more - will interact with your oscilloscope input resistance (1M), and the whole divider will be less accurate.At the same time, we must take into consideration a frequency range. The wider - the smaller resistance a divider must have (otherwise it must be compensated).

author: lukasz.kostka
author_rank: Contributor
timestamp: May 17, 2021, 02:16:12 pm
content: Unfortunately Itech doesn't provide detailed specs. I've attached manual.Ok so best would be to choose resistors >10k and < 100k ?
DC Electronic Load - Page 1
Forum section: electronics / beginners

author: KW
author_rank: Newbie
timestamp: January 23, 2019, 09:18:28 am
content: Hi...I am trying to construct a DC electronic load for a current rating from 0~5A. I found that there are different connection of resistors and capacitor at the Vout of the OP-AMP.There are two sets of designs are taken from the Kerry D. Wong's blog by changing the model of OP-AMP and MOSFET are shown in the attachments below as Figure 1 (link 1) and Figure 2 (link 2).The reference links are as below:Link 1:http://www.kerrywong.com/2017/01/15/a-400w-1kw-peak-100a-electronic-load-using-linear-mosfets/Link 2:http://www.kerrywong.com/2013/03/08/constant-current-dummy-load-in-an-hdd-cooler/What is the difference between these two designs?Kindly advise a suitable design to use in constructing a DC electronic load which has a current rating 0~5A.

author: nsrmagazin
author_rank: Regular Contributor
timestamp: January 23, 2019, 09:43:19 am
content: What is the problem with the circuit? If you are constructin the first one for 100A, I can not help you, do this at your own risk! For the second one I can help you, do this at your own risk!If its only a current load that you need, you can use a potentiometer instead, but keep in mind that your wires need to be able to support at least 6A of current.

author: MasterT
author_rank: Frequent Contributor
timestamp: January 23, 2019, 01:47:27 pm
content: Data sheet:https://www.analog.com/media/en/technical-documentation/data-sheets/1636fc.pdf

author: mvs
author_rank: Frequent Contributor
timestamp: January 23, 2019, 08:10:10 pm
content: Quote from: KW on January 23, 2019, 09:18:28 amIn older design (link2) 1nF capacitor creates local negative feedback loop for AC to avoid oscillations.In newer design (link1) he has used LT1636, opamp that can drive large capacitive loads. Compensation network (220pF and 150Ohm) is recommended in datasheet of LT1636. You can not replace LT1636 with TL071 here.PS: IRF6201 is not suitable for electronic load. You need a lateral MOSFET or even special linear MOSFET, not a trench MOSFET.It should be able to dissipate a lot of power, so you will need much better package then SO-8. Look for TO-220 or TO-247 packages and a big heatsink with fan.Typical MOSFETs that you can find in 3-5A electronic load projects are IRFP150N, IRFP260N.

author: MarkF
author_rank: Super Contributor
timestamp: January 23, 2019, 11:41:01 pm
content: Here is what I did.To have 0 to 5A range, you would need to change the sense resistor to 0.100 and have aseriousheatsink and fan.

author: not1xor1
author_rank: Frequent Contributor
timestamp: January 24, 2019, 09:17:15 am
content: Quote from: KW on January 23, 2019, 09:18:28 amthe main difference is in the compensation networkI just wonder what is the reason for using TL07* rather than, e.g., LF356From LF356 datasheet:Quote
DC Electronic Loads - Page 1
Forum section: electronics / beginners

author: tony3d
author_rank: Frequent Contributor
timestamp: October 18, 2013, 05:37:37 pm
content: Just wondering how useful Electronic loads are, and why are they so expensive?

author: npnlamp
author_rank: Contributor
timestamp: October 18, 2013, 05:43:36 pm
content: I think they are for testing and calibrating devices, like ampmeter.

author: olsenn
author_rank: Frequent Contributor
timestamp: October 18, 2013, 05:44:56 pm
content: QuoteWell, as with most things, depending on what sorts of projects you work on, they may not be useful at all. However, if you need to test a power supply (batteries, wall transformer, something you built, etc) then they can be quite useful. If you don't do this sort of thing frequently, then you can probably get away with buying a power resistor when you need it; however, if you want the flexibility of testing in CC/CR/CV/CP and/or would like a tool to automatically graph out the VI curves for you, then a DC electronic load can be quite useful indeed.I bought mine (an Itech IT8511) from ebay a while back for only $400, so they're not all too expensive unless you need something really advanced or powerful (mine only sinks 150 watts).

author: saturation
author_rank: Super Contributor
timestamp: October 18, 2013, 06:25:28 pm
content: Its main purpose, to add to olsenn's summary, is to characterize your power supply. It its simplest form, imagine a rechargeable battery you use for a flashlight. How long will it last under use? Rather than use it and find out, you can model its behavior with the eload on your bench. The Chinese have changed the pricing scheme because before that, most eloads sold were in very specialized applications and very high power handling capacity, and the limited market made them expensive. If you have an aftermarket PSU you are going to apply to a device, you can easily test its rated specs. You can find a discussion on the Maynuo, Itech, B&K, and Array in the archives.For just battery applications, there is also this, made in USA and low cost:http://www.westmountainradio.com/product_info.php?products_id=cba4If you do such tests infrequently, you can use a good power resistor and a well ventilated spot, about $20 for 100 Watts. I did so for many years, but after getting myself and wires physically burned by accident from making errors in my test set up by doing it once too many tmes, getting an eload saved me from aggravation, and injury, not to mention doing more tests under more conditions because it easier to set up and reconfigure.

author: Unknown
author_rank: Unknown
timestamp: October 18, 2013, 07:10:43 pm
content: How about theRe:load kitfor an inexpensive low-power load? Not as capable or polished (e.g. no case) as a commercial instruments, but only $20 shipped for the base model.
dc fan control - Page 1
Forum section: electronics / beginners

author: glinjik
author_rank: Regular Contributor
timestamp: January 03, 2020, 01:10:13 pm
content: hi i have tried a few of these circuits most do not work so today i got yet another circuit and tried it and it works fine very sensitive but it should not work i conected the fan to the wrong place once i realised i put the conection in the right place it then wont work? strange so i put it back to my orinal error place and all works ive highlghted where ive connected in the picture what is happening here why is it working?

author: mikerj
author_rank: Super Contributor
timestamp: January 03, 2020, 01:19:51 pm
content: You've just put a yellow square on the schematic, that doesn't tell us how you've connected the fan.If you connected the fan +v to where the yellow square is, and the -ve to ground then the fan is connected directly across the power rails. The only way the fan speed could be controlled in that case is if you have made an error in the construction and the BD140 is actually shunting the power supply and causing the voltage to drop, though this would reverse the control law

author: glinjik
author_rank: Regular Contributor
timestamp: January 03, 2020, 01:26:08 pm
content: hi sorry yes yellow square is where the fan + is the ground is as it is shown ive checked all connectios transistors in the right way round even the adjustment pot works fine i dont understand why its working

author: glinjik
author_rank: Regular Contributor
timestamp: January 03, 2020, 01:31:18 pm
content: after letting it run for a wile the bd140 starts getting a bit warm as expected
Fan issues and questions - Page 1
Forum section: electronics / beginners

author: tske
author_rank: Regular Contributor
timestamp: June 06, 2025, 04:01:27 am
content: Hi.I have a project that already built a 12cm square opening for ventilation, the problem is I cannot find a good enough fan, they are either too noisy or lack performance, or both.The performance/noise problem can easily be solved by a bigger household fan, but they are too big to fit in the enclosure.The noise are from the bearing and not the air stream. I even tried those so called "maglev" bearing fans, but they are not better at all. Why? Aren't they supposed to be floating and make no noise?Since it's not going to be portable, and I don't want to remake the enclosure, maybe I can just use a pipe to connect a bigger fan to the smaller vent hole, are there any suggestions for that?Thanks.

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: June 06, 2025, 06:29:58 am
content: Would you please elaborate on what type of fan you need? I mean, how many volts, AC or DC? Dimension?

author: indeterminate
author_rank: Regular Contributor
timestamp: June 06, 2025, 06:34:27 am
content: These are about as good as it getshttps://noctua.at/en/products/fanjust scroll down to the 120mm stuffin general the faster it spins the more noise it makes.what db(a) & air flow are you aiming for

author: tske
author_rank: Regular Contributor
timestamp: June 06, 2025, 12:13:13 pm
content: Quote from: ahsrabrifat on June 06, 2025, 06:29:58 amAnything that can fit a 12x12 cm hole.Quote from: indeterminate on June 06, 2025, 06:34:27 amLess than 42dbA, anything with max pressure and flow.

author: golden_labels
author_rank: Super Contributor
timestamp: June 06, 2025, 12:57:42 pm
content: Reduce fan speed. If normal ventilation is the goal, you shouldn’t need much. The fan barely spinning should be more than enough.If for any reason the above isn’t applicable: what noise are you hearing? Any rotating mass vibrates. This excess energy is being lost through sound and heat. So make sure the fan is securely fixed in a solid object. And that the wall itself isn’t resonating. You may consider rubber dampers to release some of the energy as heat.

author: mikerj
author_rank: Super Contributor
timestamp: June 06, 2025, 03:29:43 pm
content: Quote from: tske on June 06, 2025, 04:01:27 amUnless the bearings are failing this isn't true, the noise comes from the fan blades creating turbulence.

author: Gyro
author_rank: Super Contributor
timestamp: June 06, 2025, 04:01:53 pm
content: No point in wasting time, the OP is banned.

author: jmelson
author_rank: Super Contributor
timestamp: June 06, 2025, 11:59:53 pm
content: Quote from: tske on June 06, 2025, 04:01:27 amDell Optiplex desktop computers have incredibly quiet fans. See if you can get a replacement fan for one of these models. Some have a temp sensor in the fan so that they run at reduced speed when the heat load is small. Just look on eBay for optiplex fan.Jon
DC Grounding Circuit Undrestanding - Page 1
Forum section: electronics / beginners

author: mostatab
author_rank: Newbie
timestamp: October 13, 2021, 09:06:49 pm
content: Hi,I'm inspecting an industrial PCB which use 8 VAC voltage as input. Then a diode bridge is used in order to rectify this voltage. I've found they have used the attached circuit for the DC part of the power supply. However, I couldn't understand why they use such circuit." alt="" class="bbc_img" />Could you please explain why these circuit is used?Thanks

author: TimFox
author_rank: Super Contributor
timestamp: October 13, 2021, 09:14:52 pm
content: Are you sure that the three symbols for DC power, Ground, and Earth are correctly drawn? The circuit that you show (by itself) makes no sense.

author: mostatab
author_rank: Newbie
timestamp: October 13, 2021, 09:19:44 pm
content: Quote from: TimFox on October 13, 2021, 09:14:52 pmYes, my apology. the used symbols are not correct. the GND net is connected to negative pad of the bridge, and the Earth is connected to the chassis.

author: TimFox
author_rank: Super Contributor
timestamp: October 13, 2021, 09:31:11 pm
content: Well, C19 and C20 bypass the DC output nodes of the bridge to Earth/Chassis. The diode might prevent reverse voltage under fault conditions. C21 might be a filter capacitor (is the negative terminal of the bridge grounded elsewhere?), and the resistor a bleeder on C21.

author: radiolistener
author_rank: Super Contributor
timestamp: October 13, 2021, 10:08:36 pm
content: Quote from: mostatab on October 13, 2021, 09:19:44 pmthere is no bridge on your schematic
DC inductor from ATX transformer core - Page 1
Forum section: electronics / beginners

author: ambrozy
author_rank: Contributor
timestamp: September 25, 2022, 12:52:10 am
content: Is it possible to make a DC inductor from an old transformer core of an ATX power supply, and how? I'm not exactly begginer in electronics, but on this particular topic I am. All I know is that I need an air gap in a DC inductor, and I'm having trouble finding some good resources on designing DC inductors with ferrite core, so I would appreciate some links if there are any good online resources on the subject.

author: mag_therm
author_rank: Frequent Contributor
timestamp: September 25, 2022, 06:44:03 pm
content: Basing a design on a given available core does not need the calculations that a production inductor would need.The inductor does not have to be optimized using Hanna curves etc which is needed for production as the inductors are the major cost.For hobby, I do similar DC inductors based on surplus NOS cores, just using a simple spreadsheet.Here is a scrot of the spreadsheet for a hand wound DC filter inductor for a DC~DC converter 250 Volt 1.2 Amp that is presently on breadboard here.https://app.box.com/s/a0o4xt1nhovh3wh84ljbz5q2qmrj01ioThe choke on test:https://app.box.com/s/deaoghhngiapjlrv2tpxxtme87suhykeThe calculation uses approximations:-Core reluctance is negligible-Fringing factor is a guess at 1.2 based on experience.-The DC operating position is down from the rollover into saturation, so the a L measurement at signal generator level,will still be fairly close to the incremental inductance at operating DC level.-Conductor size is selected to be conservative by experience, avoiding the need for thermal calcs.For your specific query about references for ferrite design, I would always recommend the old book by Snelling.Member TimNJ kindly put up a link, on the ferrite gapping thread, to a non-pay copy here:https://ia803405.us.archive.org/1/items/SNELLING__SOFT-FERRITES__1969/SNELLING__SOFT-FERRITES__1969.pdfHanna DC choke curves Page 85 on,Inductor design Page 193
DC jack that disconnects internal batteries when plugged in - Page 1
Forum section: electronics / beginners

author: Cozzmo
author_rank: Regular Contributor
timestamp: August 14, 2014, 03:34:23 am
content: Is there a special name for this part?Have been asked to add an external DC power supply jack to a normally battery powered item, but still retain the battery powered possibility. To avoid issues, i'd like to use a jack that disconnects the internal batteries when the plug is inserted instead of having a switch or something. I know they exist but searching hasn't got me too far (so many items to filter through) finding anything that specifically states that it works in that way. Hoping that somewhere like Jaycar stocks them so i can just pick one up easily.

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: August 14, 2014, 03:46:23 am
content: I don't know that there is a name, its just a DC jack socket w/ 3 pins, see below example I found on google

author: jeremy
author_rank: Super Contributor
timestamp: August 14, 2014, 03:59:40 am
content: This can be problematic though, as you will lose power in the changeover. Better have some big capacitors on the power supply!

author: wyphy
author_rank: Contributor
timestamp: August 15, 2014, 01:15:11 pm
content: Don't know if it helps, but I've always heard this type of jack called a "normaled" jack, just like a relay's normally open/closed connections.

author: Refrigerator
author_rank: Super Contributor
timestamp: August 15, 2014, 03:23:12 pm
content: Type in "power jack" in google images and look from there.

author: tszaboo
author_rank: Super Contributor
timestamp: August 15, 2014, 03:53:02 pm
content: What is wrong with powerpath controllers?

author: German_EE
author_rank: Super Contributor
timestamp: August 15, 2014, 04:29:23 pm
content: As an alternative use a normal jack with diodes in series with the two voltage sources then there will be switching without loss of power.

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 15, 2014, 04:46:11 pm
content: IME, it is hard to find a power connector that does NOT have this feature. That is probably where there is no explicit mention in the descriptions.

author: dentaku
author_rank: Frequent Contributor
timestamp: August 16, 2014, 02:48:00 am
content: Looking around this room I see that every jack that's visible to me (I use them on breadboards instead of batteries) is the three pin variety that switches when you plug something into them.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: August 16, 2014, 03:49:18 am
content: http://www.jaycar.com.au/productView.asp?ID=PS0522

author: edavid
author_rank: Super Contributor
timestamp: August 16, 2014, 04:21:35 am
content: Here are some more of them:http://www.taydaelectronics.com/hardware/dc-power.html?dir=asc&order=price
DC Load Adapters - Page 1
Forum section: electronics / beginners

author: nathon
author_rank: Contributor
timestamp: March 04, 2022, 12:02:15 am
content: I just purchased a DL3031A to go with my existing home lab (see below). I'm looking to use it primarily for testing batteries and USB chargers. However, the giant binding posts have thrown me.Does anyone know if there are any adapters or boards that would allow me to go from USB to binding post or common battery connectors to binding post... or do I have to make something myself?I noticed a nice set of cables in Dave's DP832 video at about 28:25-28:46. They looked like they had interchangeable ends.https://youtu.be/Tk_3rYKWIIgExisting LabRigol DP832A - DC Power SupplyRigol DL3031A - DC Programmable LoadBK Precision 5493C - MultimeterHantek MPO6104D - OscilloscopeHP 54501A - Oscilloscope

author: thm_w
author_rank: Super Contributor
timestamp: March 04, 2022, 01:08:58 am
content: https://github.com/sirhcel/dl3000-adaptershttps://www.aliexpress.com/item/33025145386.htmlUSB low current, or make your own.

author: nathon
author_rank: Contributor
timestamp: March 04, 2022, 11:54:34 am
content: That is EXACTLY what I was looking for! Thank you so much!
DC Motor Control – Arduino for Beginners - Page 1
Forum section: electronics / beginners

author: Radhuvir_G
author_rank: Newbie
timestamp: November 20, 2014, 07:24:56 am
content: After seeing the below link.... i have an doubt.... How do I switch ON & OFF a DC fan from an Arduino?http://www.ingenstech.com/19-dc-motor-control-arduino-beginners/

author: Seekonk
author_rank: Super Contributor
timestamp: November 20, 2014, 12:47:22 pm
content: Pretty complicated for just a fan. Just drive a FET gate with an output.

author: rs20
author_rank: Super Contributor
timestamp: November 20, 2014, 01:03:51 pm
content: That code you linked there is for an H-bridge (an arrangement of 4 transistors) which can drive a motor in both forward and reverse. You just want to turn a fan on and off, so as already said, you just need a single digital pin and a N-channel MOSFET.

author: Jeroen3
author_rank: Super Contributor
timestamp: November 20, 2014, 01:09:06 pm
content: Or a relay or motor driver shield.

author: Radhuvir_G
author_rank: Newbie
timestamp: November 24, 2014, 05:26:13 am
content: thanks will look after it..

author: Kappes Buur
author_rank: Regular Contributor
timestamp: November 24, 2014, 05:43:12 am
content: After looking at examples 3 and 8, you should be able to come up with a circuit and program to start/stop a fan.
DC Motor Creates Noise in LA Battery Supply? - Page 1
Forum section: electronics / beginners

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 24, 2011, 11:57:22 pm
content: i came across a situation while try to build a power supply. when i powered a dc motor, dso showed very noise supply, i thought my circuit is noisy. but when i connected the dc motor directly to 12V LA battery, i still get the noise around 40-80Vpp, probe cable (original vs diy) did improve the situation a bit though, so i guess its something with EMP/F picked up by the probe. but how to get rid of this to minimal, say only few Vpp or mVpp? if not possible to get rid completely? whether at the LA battery supply, or PSU circuit?

author: Psi
author_rank: Super Contributor
timestamp: December 25, 2011, 04:54:27 am
content: You could install some TVS/zeners across the motor to absorb the back EMF.It wont remove it completely, just cut it off at the TVS/zener voltage.You can also try putting some caps across the motor located at the motor terminals.One cap across the motor and one cap from each terminal to the metal motor casing (3 caps total)

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 25, 2011, 02:55:38 pm
content: thanx Psi's advice. i was trying to test worst condition on the psu, i guess the motor itself is a worst noise generator. maybe putting ferrite core on the psu output will also help a little bit on its side.
DC Motor forward / reversing and limit switches question - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: March 20, 2018, 07:19:04 pm
content: I have a low RPM (planetary geared) 12V DC motor driven variometer in my LF transmitting set up, outside in the antenna loading coil enclosure. Whilst I know how to wire an in the house 3 way switch after the in house power supply, using a two core cable direct to the motor to forward and reverse it, that does not give me the over travel safety of a pair of limit switches. Is there any way to not have to use more than a two core cable to outside and have a pair of micro-switch limit switches on the variometer to stop over travel in either direction? I suspect not but have managed to get myself confused nowIf I have to use a multi cored cable, what's the minimum number of cores I need to achieve this please? Thanks for any help!

author: Andy Watson
author_rank: Super Contributor
timestamp: March 20, 2018, 08:26:08 pm
content: Is it a straight-forward DC motor - on/off control ? No PWM or such like?Just put the two limit switches in series with the motor and bridge-out each switch with an appropriately oriented diode - such that it doesn't get stuck when it runs off the end.

author: Chris Wilson
author_rank: Super Contributor
timestamp: March 22, 2018, 05:46:52 pm
content: Yes it's a basic DC motor run off a basic DC supply. thanks Andy, simple when you know how, that should be pretty straightforward to implement, appreciated!

author: David_AVD
author_rank: Super Contributor
timestamp: March 24, 2018, 11:29:05 pm
content: I think this is what you're asking for?

author: Chris Wilson
author_rank: Super Contributor
timestamp: March 24, 2018, 11:34:36 pm
content: Thanks David, that's it, I am just putting the finishing touches to the mechanical mounting of the switches, cheers!
DC Motor Sparks - Page 1
Forum section: electronics / beginners

author: geratheg
author_rank: Regular Contributor
timestamp: May 25, 2015, 07:34:23 am
content: When a low voltage DC motor is running and then disconnected at its terminals and it has no fly back diode, usually I would see sparks across the wire and the motor.My questions are:1) Are these sparks the result of the DC motor being an inductive device?2) Are they avoided with a diode?3) Are these sparks high voltage sparks (read it takes thousands of volts to break down the ions in the air?)

author: jeristair
author_rank: Newbie
timestamp: May 25, 2015, 08:12:50 am
content: The sparks are because the motor appears (from an electrical view) as an inductor.Turning off the motor causes the current to suddenly stop, therefore the inductor will create a large back emf

author: Seekonk
author_rank: Super Contributor
timestamp: May 25, 2015, 08:15:43 am
content: YesNot necessarilyIt doesn't take thousands. Arc welders work at about 35V. You should pick up a copy of GASEOUS CONDUCTORS, the bible of things that go arc in the night by James Dillon Cobine.

author: macboy
author_rank: Super Contributor
timestamp: May 25, 2015, 12:29:01 pm
content: Quote from: geratheg on May 25, 2015, 07:34:23 am1. Yes2. No, you use capacitors across the motor terminals to prevent the sparking. A snubber may be better (some series resistance as either ESR of the cap, or added as a resistor), but a simple capacitor will do. Often two small caps are used, one from each terminal to the motor can.3. Yes, suddenly interrupting current to an inductor such as a motor coil will produce a "high" voltage spark. How "high" the voltage is will depend on how much is needed to generate the spark (distance to the conductor).

author: geratheg
author_rank: Regular Contributor
timestamp: May 25, 2015, 03:19:52 pm
content: A flyback diode won't prevent the sparks? Would the diode just short the terminals of the motor in one direction thus preventing the sparks?
DC motor stall current - Page 1
Forum section: electronics / beginners

author: init
author_rank: Contributor
timestamp: October 15, 2016, 02:25:29 am
content: Hey guys, possibly rookie question here. I have a motor:https://www.motiondynamics.com.au/worm-drive-motor-12v-50w-45-65-rpm-5-29nm-torque.htmland have measured the resistance to be around 5 Ohms. The recommended operating voltage is 12V, so that would imply the maximum or stall current would simply be 12/5 = 2.4 A ish but the website says the stall current is 30A. How is this possible? Are they over driving the voltage?

author: init
author_rank: Contributor
timestamp: October 15, 2016, 03:13:44 am
content: Quote from: blueskull on October 15, 2016, 02:35:27 amIf this is worst case, does this imply I can drive the motor at this worse case for long periods? If not, how long is acceptable? I measured the resistance between the input terminals while the motor was off with a basic $40 multi meter, I'm guessing I may need something that gives a more accurate reading, or was I attempting to measure resistance incorrectly?

author: init
author_rank: Contributor
timestamp: October 15, 2016, 03:42:06 am
content: Quote from: blueskull on October 15, 2016, 03:21:35 amFrom every permutation of resistance measurement, the ones which were less than 200 Ohm were 0.3, 4.6, 24.5 Ohm. It doesnt help that the wire colors dont match up with what the schematic diagram says, so I'm not sure what I am measuring across.

author: init
author_rank: Contributor
timestamp: October 15, 2016, 03:52:33 am
content: Quote from: blueskull on October 15, 2016, 03:49:34 amSorry I mean the same wire colors are there but they are in different locations in the housing. Thanks for the help BTW.
DC motor with PWM control - Page 1
Forum section: electronics / beginners

author: salty
author_rank: Newbie
timestamp: September 22, 2022, 12:38:25 am
content: Hello, My project is to convert a treadmill drive to run a wood lathe. My problem is that as soon as I connect the drive belt the over current indicator light on the circuit board lights up and the motor will run at slow speed for awhile before bogging down making a loud hummming noise. Without the drive belt it runs normal. I have had the brushed motor apart and cleaned up the commutator on my metal lathe then ran it at high speed ( belt off) for 10 minutes to seat brushes. Voltage to motor without belt is 30 to 85 volts full speed. With belt it starts at 30 will maybe reach 35 before it bogs. I have converted these drives before and one thing different about this system is the lack of choke coil. There is just a short jumper wire in its place. I'm not sure what the choke does but would like to be educated about its use. Also there is a small unit (they call it a reed switch ,pulsing 5V ) that is triggered by a magnet on the original belt drive.In other installations I've ignored this and they have worked fine. Thanks

author: mjkuwp
author_rank: Unknown
timestamp: September 23, 2022, 10:49:32 pm
content: are you giving it some kind of speed command? is it possible that simply, the load put on the motor causes it to be over-current and the drive is responding as it should? You may need to put the reed switch close to the pulley - and of course a magnet in the pulley to give the drive the speed feedback it is expecting.What RPM do you need to go? I guess you know this but a higher belt ratio would be required to keep the current low and voltage high (speed the motor up)I don't think a choke would affect the motor bogging down or not. Things like that are used to pass EMI testing.

author: WattsThat
author_rank: Frequent Contributor
timestamp: September 24, 2022, 01:17:26 am
content: What are specs of the PWM source you’ve purchased?Typical treadmill motors are rated for 0-120volts dc, perhaps even 150 max at 1000 watts or more so you need to match those voltages and have at least 8-10 amps available to get to those torque and power levels.Do you have a multimeter?

author: salty
author_rank: Newbie
timestamp: September 26, 2022, 04:06:09 pm
content: It starts on it's slowest speed and the overcurrent light is on. It will run at this speed for awhile but eventually bogs down. Speed increase will hasten failure. The load on the unit is a V-belt turning a spindle in good ball bearings, not much compared to an 18 inch belt with a 250 pound person walking on it.I can try to mount the reed switch but it runs fine without it in a no load situation and on other conversions I have done.The unit is described as a MC-1000 SCR Motor controller.The motor is rated at 0 -95 V and when it is run up to full speed (belt off) it develops 85V.Could there be a weakness in the motor armature windings and how would I test this?I have a Fluke multimeter
DC motor - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 02, 2014, 11:24:49 pm
content: Hi,What is the meaning of gf-cm 11.7 in the starting torque colum.What is the relation fo Joules to the torque and watts.How can we measure that in reality?Some specs define the power as (Ex: .033Joules).In the first column:238mA * 5 volts = 1.19 WattLoad speed 6258 rpm.The first turn should take 1*60/6238 = 0.0096184674575184353959602436678423 secIf a Joule/s is a watt. WE should have 1.19*0.0096184674575184353959602436678423 = 0.0114459 joulejp

author: IanB
author_rank: Super Contributor
timestamp: April 02, 2014, 11:50:17 pm
content: gf-cm is "grams (force) by centimeters"It is a measure of the maximum torque the motor can apply when stationary and starting to move.At this time the motor is delivering no shaft power (since the output shaft is stationary), but it is consuming considerable electrical power. Therefore the efficiency of the motor under these conditions is zero. Needless to say the motor will get hot if it remains in this state for too long.Electrical power is measured as volts (force) times amps (rate of movement).Mechanical power in a shaft is measured as torque (force) times rotational speed (rate of movement).Units of measure are important. For instance if torque is measured in Nm (newton-meters) and rotational speed is measured in radians per second, then power will be in watts.Note that when the motor is turning at its normal speed the torque will not be the same as the starting torque.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 03, 2014, 12:44:14 am
content: I will have.0011N/m * pi *rad /.06sec =

author: IanB
author_rank: Super Contributor
timestamp: April 03, 2014, 01:39:05 am
content: The information is all there in the motor specifications:For instance, the rated load voltage is 5.0 V and the rated load current is 77 mA. That means the rated input power is:5.0 x 77 = 385 mWThe rated load speed is 6258 rpm and the rated load at this speed is 0.3 mN-m.Convert rpm to rad/s:6258 / 60 x 2 x pi = 655 rad/sHence the shaft output power is:0.3 x 655 = 197 mWThus we can calculate the efficiency:197 / 385 = 51%It doesn't seem too good perhaps, but then it is a miniature motor...

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 03, 2014, 01:47:51 am
content: I feel better)
DC MOTORS , FIND THE NO OF POLES - Page 1
Forum section: electronics / beginners

author: WiredSmart
author_rank: Contributor
timestamp: December 12, 2022, 06:12:06 am
content: Im looking at a motor and on the name plate i have the following info:RPM:1500kw 0.125FRAME 80SER NO H166REF NO 1602050ENCL IP44B3Made in SAI would like to know how I can be certain how many poles this motor has, is this done visually, with a formula . The name plate does not tell how many poles it has

author: Gyro
author_rank: Super Contributor
timestamp: December 12, 2022, 10:09:39 am
content: The only motors that you can tell the number of poles on is an AC induction type. It's not possible with brushed AC or DC motors.You ether need to be able to count the poles by looking through ventilation slots (if you can) or find the original manufacturer data....Actually, one other possible method. If the brushes are removeable, you might be able to do it by counting commutator segments, there should be one segment per pole. With a significant number of poles it could be tricky though - you need good light and you either need to be able to accurately mark the starting position of the armature, or the first segment you counted.

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 12, 2022, 10:57:55 am
content: As Gyro said it's hard to find out and it's not listed on the nameplate because there isn't a need to know how many poles in a DC motor.
DC offset for measuring capacitors - Page 1
Forum section: electronics / beginners

author: slashguitar
author_rank: Contributor
timestamp: December 12, 2011, 01:32:10 pm
content: Hello,I want to build an autoranging LCR meter for my graduation thesis (similar to Smart Tweezer). I will use the I-V method described by Dave in his "bonus tutorial".The problem is that i don't know what to do with polarized capacitors. Do I need an offset voltage or if the ac test signal is small enough(<1Vpp) the capacitor isn't affected?thanks

author: don.r
author_rank: Frequent Contributor
timestamp: December 12, 2011, 05:25:15 pm
content: You can either bias it with a small DC (make sure its the right direction!) or not bother with DC and let the cap ride the AC. As long as your frequency is high enough there should be zero voltage drop across the cap so no worries. Many audio circuits use polarized electrolytics as decoupling caps.

author: Zad
author_rank: Super Contributor
timestamp: December 13, 2011, 03:22:54 am
content: It shouldn't cause any issues at low voltages. Having said that, the LCR meter the I'm developing has a programmable offset, but that's mostly to trim the drive signal to match the transimpedance amplifier which is internally set at Vcc/2.Lots more waffle on the subject on my blog starting here:http://electronicsdesigner.blogspot.com/2011/03/design-for-precision-lcr-meter-aka.htmlhttp://electronicsdesigner.blogspot.com/2011/04/design-for-precision-lcr-meter-part-2.htmlI should say that things have moved on since then, and I'm currently writing an update. Are you building a totally from-scratch system or using something like the AD5933?

author: Zero999
author_rank: Super Contributor
timestamp: December 13, 2011, 09:33:07 am
content: I certainlt wouldn't be worried about damaging the capacitor under test. The only reason I can see for a bias voltage is to test the voltage vs capacitance characteristic - some dielectrics vary their permittivity as the bias voltage changes.

author: slashguitar
author_rank: Contributor
timestamp: December 14, 2011, 10:28:55 am
content: Thanks for the answers guys@ZadI read your blog a while back and really liked the way you explained things. Waiting for part 3 on the LCR meter.Considering it's a graduation thesis I want to build the LCR meter from scratch so I can "show off" the "analog skills" I acquired during university rather than using an of the shelf IC which does pretty much everything for me( have to impress the teachers to get a good grade )
DC offset voltage measurement - Page 1
Forum section: electronics / beginners

author: sahko123
author_rank: Frequent Contributor
timestamp: April 07, 2020, 01:51:42 am
content: for an amplifier im designing i want to know the dc offset on a signal as a 1:1 output voltage (a circuit that outputs the dc offset voltage without the signal). My idea was to have a differential amplifier set up as a buffer on either side of an ac coupling capacitor. Would this make sense as an applicable circuit? or are there better ways of getting the desired result?

author: David Hess
author_rank: Super Contributor
timestamp: April 07, 2020, 02:08:24 am
content: I think you mean an instrumentation amplifier and not a differential amplifierWhat you suggest can work and is common with DC servo circuits which correct DC offset of an amplifier. RC lowpass filters are applied to the input and output and then an amplifier measures the resulting DC difference. Typically a low input bias current amplifier is used so that the filter time constants can be as long as possible with reasonable values of resistance and capacitance.

author: sahko123
author_rank: Frequent Contributor
timestamp: April 07, 2020, 02:12:19 am
content: when i said differential amplifier i meant that ill have something at either end of an rc highpass filter (at a frequency beyond what i need like 30khz or something arbitrary) that measures the difference between the voltages at either end of the capcitor

author: Zero999
author_rank: Super Contributor
timestamp: April 07, 2020, 01:06:13 pm
content: You need a low pass filter to get the DC offset. It's not clear what you're talking about. Please post a schematic.

author: sahko123
author_rank: Frequent Contributor
timestamp: April 07, 2020, 04:08:39 pm
content: Because of how low the frequency of the signal is (audio 10hz to 20khz) i would need an ac coupler the basic circuit concept is as pictured. As far as i know its essentially performing common mode rejection to get the dc bias.
DC Offset - Page 1
Forum section: electronics / beginners

author: thedoc298
author_rank: Contributor
timestamp: April 15, 2018, 12:17:44 am
content: Does anyone know if it is possible to adj the dc offset of the FeelTech fy6600. What I mean, is the display is 113 mv off of what I set it to. If I set it to 0 volt offset it still outputs .113 volts dc. Need to calibrate the internals to match the screen.
DC panel meter uncertain of the wiring. Hoping for some suggestions - Page 1
Forum section: electronics / beginners

author: golash
author_rank: Contributor
timestamp: April 12, 2015, 09:27:19 pm
content: HiI have this panel meter and I`m uncertain from the diagram which wires go the load. And whatwires power the panel meter`s electronics. It seems the meter has 3 wires but the pic shows 4 wires.http://www.ebay.com/itm/111275976827?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

author: TimFox
author_rank: Super Contributor
timestamp: April 12, 2015, 09:34:24 pm
content: You apply DC supply voltage for the meter electronics between the two wires on the right. The negative terminal on the power supply (battery or whatever) is common to the negative terminal of the measurement voltage.The voltage being measured is applied between the two wires on the left. Again, note that the negative terminal is common to the power supply negative, which normally would be grounded external to the meter.

author: Seekonk
author_rank: Super Contributor
timestamp: April 12, 2015, 10:15:20 pm
content: Just make sure you don't power it with more than 28V. I will often source the positive power through a resistor if more than 12V to drop the voltage down and prevent line spikes from damaging the meter. 100 ohms is a good start and place a 100uf or greater at the meters red and black wires for filtering.The current meters are trickier to install as they sense current in the negative lead for convenience of measuring low side voltage and sometimes it isn't easy to isolate common.
DC power connector choice - Page 1
Forum section: electronics / beginners

author: netdudeuk
author_rank: Frequent Contributor
timestamp: March 13, 2022, 10:48:57 am
content: HiAm I correct in thinking that this power connectorhttps://www.ebay.co.uk/itm/304392340491?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D94d80b9778ad4f758248d31668daab89%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D304392340491%26itm%3D304392340491%26pmt%3D1%26noa%3D1%26pg%3D2380057%26brand%3DUnbranded&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3Aa84a2172-a2ba-11ec-90a8-b28fdcdb8470%7Cparentrq%3A82e1cf9917f0ab969ba7ec29fffa281e%7Ciid%3A1is the correct size for this power supply ?https://uk.rs-online.com/web/p/ac-dc-adapters/1753322Thanks

author: nvmR
author_rank: Regular Contributor
timestamp: March 13, 2022, 12:01:05 pm
content: Seems correct - both 2.1mm (inner) and 5.5mm (outer)There are cheaper options for panel mount dc jacks though, with less plastic - the simple circular ones, if you would like to reduce costs.https://www.aliexpress.com/item/32985876868.htmlhttps://www.aliexpress.com/item/1005001730846577.htmletc.

author: Ian.M
author_rank: Super Contributor
timestamp: March 13, 2022, 12:42:01 pm
content: The power jack you found on Ebay is of a type that I and many others wouldn't trust for high currents. Generally power jacks with a single side contact for the barrel should only be used for a maximum of 2A, not sustained,even if their nominal ratings are higher! As your PSU is rated for 2A, and the jack in question obviously has a thermoplastic moulded body/mounting plate, this could be problematic.The first jack 'nvmR' linked has much better barrel contacts. Its collet style, making contact all the way round, suitable for the highest currents this sort of jack can be used for.The second has a metal body, which is more robust, but problematic if you have a metal panel and don't want the barrel grounded.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: March 13, 2022, 04:59:56 pm
content: Quote from: Ian.M on March 13, 2022, 12:42:01 pmThanks both. I'll probably get some of the first item to be listed.

author: Terry Bites
author_rank: Super Contributor
timestamp: March 13, 2022, 05:08:44 pm
content: Are you a Switchcraft fan?

author: netdudeuk
author_rank: Frequent Contributor
timestamp: March 15, 2022, 05:43:52 pm
content: Quote from: Terry Bites on March 13, 2022, 05:08:44 pmI'd not previously heard of them but I've now found similar items listed online thanks.
DC Power Failure Alarm - Page 1
Forum section: electronics / beginners

author: Pariston
author_rank: Contributor
timestamp: April 19, 2021, 11:13:16 am
content: Hi,I've been looking for some DC power failure alarm system for my circuit. Input power is 36 volt and I'd like my mcu to react to sudden drop in voltage. What are the most reliable/long lasting ways of power loss recognition in a dc circuit?

author: mhuber1
author_rank: Newbie
timestamp: April 20, 2021, 07:47:39 am
content: I'd use a schmitt-Trigger with a voltage divider hooked up to an interrupt pin of the mcu

author: mvs
author_rank: Frequent Contributor
timestamp: April 20, 2021, 12:39:42 pm
content: GPIO inputs of most MCUs do have some hystheresis and more or less constant threshold levels, so you can connect voltage divider directly to the interrupt pin.You may need a debounce procedure in software for proper operation (i.e. to avoid interrupt storm).If you wish to have exact threshold, you can use voltage comparator. Some MCUs do have built in comparators.Third option is ADC. It is usually slower and less reliable, but you will get a voltage value to play with.

author: thinkfat
author_rank: Unknown
timestamp: April 20, 2021, 12:47:56 pm
content: I would advise also to immediately shut off peripheral ICs to preserve some juice for the MCU.
DC power jack shows voltage in 3rd pin when plugged in? - Page 1
Forum section: electronics / beginners

author: geratheg
author_rank: Regular Contributor
timestamp: August 22, 2014, 07:26:40 pm
content: I have a few DC power jacks of various sizes and shapes with 3 pins, 2 of them are connected when not plugged in, 1 is isolated for positive. When a plug is plugged into the jack usually the 2 that were connected disconnect, one goes to negative, the other - which I will call the third pin - isn't connected to anything. This is true for all power jacks and none of them show voltage in the third pin except for one.That's strange, where is this voltage coming from to the third pin if the pin is disconnected? Is this something to worry about and should I get a new adapter?This is a picture of the adapter that shows voltage, I only have one piece:5.5mm x 2.5mm DC Power Jack

author: SeanB
author_rank: Super Contributor
timestamp: August 23, 2014, 05:43:16 am
content: Likely leakage through the phenolic insulation.

author: dr_dan
author_rank: Contributor
timestamp: August 23, 2014, 07:16:01 am
content: The jack might be faulty - check for shorts between the two pins.This third contact is only used to disconnect a battery when the supply plug is inserted. If you don't need that functionality, the jack will be fine as it is.