hybridfree/eevblog-posts huggingface dataset:
3v radio, but only 3.3v or 2.7v supply available - which to use? - Page 1
Forum section: electronics / beginners

author: Delta
author_rank: Super Contributor
timestamp: June 25, 2015, 01:52:56 pm
content: I've got a cheapo AM/FM portable radio (a transistor radio as my grandparents would say 😀 ) that runs off two AA batteries. I want to bodge it so I can run it off a 5v USB plugpack, but I only have 3.3v linear regulators on hand.So should I run it at 3.3v and assume there's nothing in it that can't tolerate .3v overvoltage, or stick a diode in series and assume it should work fine at 2.7v? (which I'm sure it will, if it was designed to take rechargables...)Cheers!

author: Augustus
author_rank: Regular Contributor
timestamp: June 25, 2015, 03:02:28 pm
content: A device, designed to operate on two AA batteries in series is very unlikely to get toasted, if hooked up to a 3.3v supply, given the fact that fresh batteries are in the range of a healthy ~1.6v per cell, depending on used chemistry. I think it's a safe bet to assume that this thing will quite happily run on 3.3v...

author: Delta
author_rank: Super Contributor
timestamp: June 26, 2015, 03:16:44 pm
content: Cheers for that mate. I've stuck in a 3.3v PNP LDO, with 10uF across each side, and it seems quite happy. The radio says 100mA max, so I've worked out that the LDO will not be dissipating more than 170mW - that should be fine for a TO92 package, yes?Incidentally, I've found that Apple USB chargers (the small ones for iPhones) are ridiculously noisy - AM reception was impossible! It's fine though with an Amazon one though (which came with a Kindle Fire - which is a piece of shit but at least has a clean plugpack!)Thanks again.

author: cpt.charlie
author_rank: Contributor
timestamp: June 27, 2015, 12:24:15 pm
content: If you need a little vdrop, you can use an shottky diode in series with the load, BTW the noise on the apple charger could be normal if the charger is a fake Chinese unit.

author: Delta
author_rank: Super Contributor
timestamp: June 30, 2015, 10:34:08 am
content: The charger is genuine apple - it came with the missus's iphone!

author: flynwill
author_rank: Regular Contributor
timestamp: June 30, 2015, 01:23:41 pm
content: Well I wouldn't blame Apple... The charger wasn't design with powering an AM radio in mind, and the AM radio was designed to run from batteries and not from a switching power supply. It wouldn't surprise me if the switching in the little Apple converter landed smack dab on top of the radio's 455 kHz IF, or somewhere in the AM band.
3VDC 2A power supply - Page 1
Forum section: electronics / beginners

author: laudrup
author_rank: Newbie
timestamp: July 22, 2014, 01:55:36 pm
content: Hi,I am trying to buy an ac adapter to hook up a Rosahl MDL-3 dehumidifier. The power supply requirements are listed here on page 2 for the device:http://www.rosahl.co.uk/wp-content/uploads/2013/02/RB-OP09001AMDL-instruction-manual.pdfThe problem I am having is that most of the ac adapters available at Jaycar or on the internet don't go into this level of detail on their specifications.I came across the following 3V 2A ac adapter on eBay.http://www.ebay.com.au/itm/BRAND-NEW-3V-2A-AC-DC-Power-ac-adapter-Power-supply-/290565341956?pt=AU_Electronics_Batteries_Chargers&hash=item43a70b4304&_uhb=1Again the specs are not really specific, but based on people's knowledge of these kinds of devices do you think this is likely to meet the specifications for the dehumidifier?(I am going to have the dehumidifier attached to a plug and play humidity controller that measures the humidity in a chamber and then switches the plugged in device on or off depending on this measurement)Many thanks.

author: Paul Rose
author_rank: Regular Contributor
timestamp: July 23, 2014, 11:46:50 pm
content: The key requirement on the dehumidifier is the over current protection.The hint is that fold back style may not work.This probably means that the element will "try" to draw more than 2 amps initially and draw less as it gets going.Constant-current style limit supply will limit the current to 2A by lowering the voltage and increasing it as the current draw lessens.The foldback style may get stuck low after the initial overload, which is good protection for the pass transistor in the supply, but not useful for this particular application.The e-bay listing only says that there is overload protection, so you can't tell.A clue is that it supports 100-240v input, so it is very likely a switcher. Maybe somebody will know what style of current limit typical wall-wart switcher uses.
3W LED Driver - Page 1
Forum section: electronics / beginners

author: Zinger
author_rank: Contributor
timestamp: May 16, 2021, 09:21:58 pm
content: I need a small form factor constant current driver for a 3W RGB or RGBW LED. It should run off 5 or 12 volts and be controllable with logic level signals from an Arduino. A 3W RGBW LED with built-in driver would also work.My project is pretty small. I need to fit the driver, LED and Arduino Nano or similar microcontroller in a 3" x 3" 3/4" case. It's for a desk lamp for a friend.I've found several parts that work for lower power LEDs, some I2C parts that are close and a few that are overkill for what I need. But nothing small and easy to wire for a single 3W LED.Any suggestions? I'm more comfortable working with logic level circuits. Something that needs a lot of external components for EMI etc. is probably beyond me.

author: Marco
author_rank: Super Contributor
timestamp: May 16, 2021, 10:02:29 pm
content: I'd useinverting buck boost with just the PWM channels from the micro. Inverting buck boost in discontinuous mode at a constant duty cycle and supply voltage will act like a constant power driver, which is just as good as a constant current driver, no need for a sense resistor even.PS. that link was just the first write up I found of the concept, you cangooglemore. Boost at constant duty cycle can also work as a constant power driver by the way, but that's not really relevant here.PPS. might want to use RGBWW LED. RGB is nice for mood lighting, but white LED will have better CRI ... so a little more white is probably better.

author: Zinger
author_rank: Contributor
timestamp: May 20, 2021, 02:00:51 pm
content: The Adafruit Pixie is just what I need. It's 3W RGB. Has built-in constant current supply and color control. It's small enough to fit in my project and has over-temp protection. The current supply is linear instead of switched but for this form factor and price I'll accept a little extra waste heat. I need to weight my base so it doesn't tip over. Might as well use that as a heat sink.https://www.adafruit.com/product/2741
4-20 mA current loop - Page 1
Forum section: electronics / beginners

author: Fatih
author_rank: Newbie
timestamp: July 09, 2013, 07:35:02 am
content: How are lower (4 mA) and upper (20 mA) boundries determined? I have found that zero offset of the base current (4 mA) makes cable break detection simple. However, I did not understand why it is 4 mA in the first place? I guess it is a optimal value found after some calculations, and I want to understand the logic behind it. Same goes for 20 mA.Thanks in advance.FatihEdit:I do not want to be argumentative. I mean, I do not say why it is 4 mA or 20 mA, and not something else. What I am asking is not about mere numbers, but why it is preferable over other current values. I hope I made myself a bit more clear. I appreciate any further edit advice for clarifying the question.

author: Rerouter
author_rank: Super Contributor
timestamp: July 09, 2013, 08:06:25 am
content: it may have been a case of chicken and egg, as 1-5V signalling was used around the same time frame, which over 250 ohms becomes 4-20mA

author: chibiace
author_rank: Regular Contributor
timestamp: July 09, 2013, 09:33:19 am
content: Four and twenty current loops are pretty popular in industrial 24v setups

author: komet
author_rank: Unknown
timestamp: July 09, 2013, 09:33:40 am
content: The lower bound was chosen to be enough to power a reasonable sensor. The upper bound was chosen to be low enough to not cause a spark, so that the interface can be used in explosive environments. Apart from that, standard values like this are never arrived at by calculation, but by compromise and tradition.

author: SeanB
author_rank: Super Contributor
timestamp: July 09, 2013, 06:24:31 pm
content: There are other current loops as well, common being the 10-100mA ones sometimes used in process control, and of course the 600R loop used in telephony, which was actually accidentally standardised as it was the resistance of the first earpiece AG Bell wound to use in the experiments.

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: July 10, 2013, 12:04:20 pm
content: Actually it has more to do with ohm's law than anything else:http://www.bapihvac.com/content/uploads/2010/07/Designing-4-20-mA-Current-Loops.pdf< section on load resistor

author: glatocha
author_rank: Regular Contributor
timestamp: July 10, 2013, 11:48:16 pm
content: Probably worth to notice here is that standard allows to go slightly under 4mA and slightly over 20 for underrange and overrange.In Simens S7 PLC series the analog inputs thouse values are something like ~3 mA and 22mA
4-20ma current loop receiver - Page 1
Forum section: electronics / beginners

author: Kemme
author_rank: Contributor
timestamp: September 21, 2015, 05:26:15 am
content: Hello allCurrent loop receivers are bascially resistors and opamps which amplify the voltage across the resistor. Right?Is there any standard which defines the value of the resistor in professional devices?

author: bobcat
author_rank: Regular Contributor
timestamp: September 21, 2015, 11:00:43 am
content: The value of the resistor depends on the voltage required by your receiver amp. Using V/I=R. There is no standard maximum voltage that the transmitter can develop to drive the loop. Some typical voltages are 36, 24, 15, 12, some phone systems use 150 volts! Look at the specs on the transmitter.

author: Rerouter
author_rank: Super Contributor
timestamp: September 21, 2015, 11:08:59 am
content: A generic one used is 250 ohms to translate to to 1-5V, however it can be as small as you like if you trust your op amp will not introduce too much noise into the amplified signal,Otherwise i have come across a number of devices where the input was a current mirror, meaning it was more or less a fixed voltage drop,The general process is to have your input stages isolated from one another, as there is no telling where in the chain it will sit, most devices are specced up to a maximum of 48V, and for the resistor types, if you know you maximum voltage drop for the signal range, many designs incorporate a zener or bypass diode, so that in the event of grossly excess current it will be shunted through a power diode as opposed to your high spec resistor,

author: Kemme
author_rank: Contributor
timestamp: September 21, 2015, 05:27:12 pm
content: I am actually creating a current loop transmitter with maximum output voltage 20V so the maximum load resistance (I mean cables and receiver) is 1kOhm. I was just curious how close to the edge I am.Thanks for answers.

author: HeiBau
author_rank: Newbie
timestamp: September 26, 2015, 07:19:07 pm
content: Check ISA50. With 1 kohms load you are over the edge, as 800 ohms is the maximum allowed load.For testing your system seehttp://www.divize.com/current-loop.htmlRegards,
4-20mA Current Loop to Bluetooth Project. - Page 1
Forum section: electronics / beginners

author: BrianOShea
author_rank: Newbie
timestamp: October 23, 2019, 06:42:52 pm
content: Hello!I'm new to this and not quite sure how to proceed.I'm looking to connect an analogue moisture sensor running off a 4-20mA current loop to my android tablet via some sort of Bluetooth setup for monitoring.I'd like to keep this project as simples possible as I don't know much about Bluetooth or app building.I've looked around the internet at different circuit boards with Bluetooth from Arduino and a few others but they seem pretty advanced for my needs.Does anyone have a simple, cheap, low power solution?Also, once connected via blue tooth how do I display the meter readings on my tablet, do I have to get into coding or is there an app that can do this for me?Thanks.Brian

author: ebclr
author_rank: Super Contributor
timestamp: October 23, 2019, 10:34:57 pm
content: If you wana buy one here we gohttps://au.omega.com/pptst/OML-TM_OML-RM.html
4-bit ADC on a microcontroller - how to avoid "in-between" numbers - Page 1
Forum section: electronics / beginners

author: Saimoun
author_rank: Frequent Contributor
timestamp: July 31, 2020, 11:39:00 am
content: HiI have an STM32 uC which needs an (audio) volume control. The audio is done by an IC (LM4811) which has 16 discrete volume levels of 3dB each, which I can control from my uC.I thought I would use a simple 100k'ish potentiometer with an ADC. This works great, I put a 6-bit ADC on and I divide the result by 4, so I get values from 0 to 15 which I can send to the audio IC.My problem is if you put the potentiometer precisely between let's say 7 and 8, I will alternatively get 7 and 8, constantly, which might be annoying for the listener as the volume will keep jumping up and down.CheersSimon

author: free_electron
author_rank: Super Contributor
timestamp: July 31, 2020, 12:21:06 pm
content: don't divide. Only use top 4 bits of the adc to control the gain.use the lowest 3 bits of the ADC as hysteresis. : 110 : change up. 001 : change down. any other state : do nothing.

author: Saimoun
author_rank: Frequent Contributor
timestamp: July 31, 2020, 12:56:12 pm
content: That sounds great thanks but can you explain a bit more? It's only a 6-bit ADC though, so only 2 extra bits - but I can also configure it to be 8 or even 12 bits.In particular, how do you make sure you do not miss any values?

author: Ian.M
author_rank: Super Contributor
timestamp: July 31, 2020, 01:10:29 pm
content: The basic algorithm is:Code:Read ADCIf (abs(ADCvalue - OldValue) > HYSTERESIS)Write POTOldValue := ADCvalue & POTMASK // masked to only 4 bits used by pot, but *not* shifted.Endifwrapped in your superloop. Initialise OldValue and the Pot to zero.Try with the HYSTERESIS #defined as half the interval between Pot increments. Depending on the ADC noise level you may need to increase or reduce it, but it must *NEVER* be zero, or greater than or equal to the pot increment.

author: Saimoun
author_rank: Frequent Contributor
timestamp: July 31, 2020, 02:20:30 pm
content: That works great! Thanks

author: David Hess
author_rank: Super Contributor
timestamp: August 01, 2020, 01:17:41 am
content: Old Tektronix DSOs faced this problem with poteniometers used as digital encoders and they did exactly what is suggested with hysteresis. The way they did it works better than many modern encoder implementations.

author: Saimoun
author_rank: Frequent Contributor
timestamp: August 02, 2020, 08:21:44 am
content: It works beautifully - even with the pot on the breadboard!
4 bit adder problem - Page 1
Forum section: electronics / beginners

author: Fuldup
author_rank: Contributor
timestamp: May 13, 2024, 08:04:48 pm
content: Hi i started simulating a 4 bit adder made out of NPN transistors and i got a problem with the and gate on the right, which schould give a signal only if both the inputs are on, in the screenshot below you can see that just 1 input is high and the current still go through, it is just 387.9μA but it's enough current to activate the second XOR-gate what should i do to fix this problem?

author: CountChocula
author_rank: Unknown
timestamp: May 14, 2024, 01:26:59 am
content: You're trying to use the AND gate to source current into the base of one of your OR gate's inputs, and it's going to be really hard to control the amount of current that flows when the AND gate is off, because the input impedance of the OR gate will affect it.It's easier if you think of each gate as an individual building block that connects directly to the two rails and produces an output from them. This allows you to manage the flow of current more easily, because you can control the impedance of each output to ground, and thus create a preferential path for the current to follow when a gate is shut off. For example,this circuitimplements two AND gates feeding into an OR gate, whose output is then inverted by a NOT gate. As you can see, there is still stray current in the circuit (that must be the reason why all those TTL chips tend to get so hot), but it's easier to control because each gate is independent from the others.I'm sure more experienced folks on the forums will be able to provide better solutions/explanations, but I hope this helps a bit. Cheers!—CC
4-bit leading one detector? - Page 1
Forum section: electronics / beginners

author: tiofilo75
author_rank: Contributor
timestamp: June 23, 2012, 11:22:17 pm
content: Hello everyone. This is my first post. I am currently going to school and am having some trouble understanding one of my assignments. I have tried Google but I am still confused. So I am suppose to come up with a Boolean function that detects the leading ones in 4 bits. Can some one please shed me some light?I know about kmaps, I just dont know how fill up the rest of the truth table. What exactly is a "leading one detector"? What exactly are my Z , L1 and L2 outputs?Ok, I figured out that the L1 and L2 give the position of the leading 1 in binary. I just need to figure out what Z is.

author: chrome
author_rank: Regular Contributor
timestamp: June 23, 2012, 11:32:02 pm
content: http://en.wikipedia.org/wiki/Karnaugh_maps

author: Psi
author_rank: Super Contributor
timestamp: June 23, 2012, 11:57:41 pm
content: A leading one detector just provides the position of the first 1.The word "leading" indicates your looking for the first one starting from the MSB and moving right towards LSB.(A trailing one detector would look for the first 1 starting at LSB moving left to MSB)So, using the existing middle line of the truth table as an exampleB3 B2 B1 B00 1 1 1Starting from the MSB, B3 (0) and looking for the first one we find it in the B2 position.B2 = 2 which is 10 in binary, so (L1=1 L0=0)

author: olsenn
author_rank: Frequent Contributor
timestamp: June 24, 2012, 12:01:43 am
content: It looks to me like what this system is described by the following relationship:If B0, B1, B2, and B3 are 0, Z=1, and L1/L2 don't matter. Otherwise, Z=0If Z=0, the number L1L0 = the most significant bit that is 1So when B3 B2 B1 B0 == 0 0 0 1, B0 is the MSB that is 1, so L1 L0 == 0 0 (0 in decimal)when B3 B2 B1 B0 == 0 1 1 1, B2 is the MSB that is 1, so L1 L0 == 1 0 (2 in decimal)when B3 B2 B1 B0 == 1 1 1 0, B3 is the MSB that is 1, so L1 L0 == 1 1 (3 in decimal)when B3 B2 B1 B0 == 1 1 1 1, B3 is the MSB that is 1, so L1 L0 == 1 1 (3 in decimal)... In theory, if B3 B2 B1 B0 == 0 0 1 0, or 0 0 1 1, B1 would be the MSB that is 1, so L1 L0 would be 0 1 (1 in decimal)Hope this helps!

author: Tony R
author_rank: Regular Contributor
timestamp: June 25, 2012, 11:37:57 am
content: If we did this for you you would not learn...so this here are some tips1) complete the truth table with all 16 values. (by observing the truth table the L1 and L2 are your most significant one.) and z means zero.0001 => 00001x => 0101xx => 021xxx => 03now that I think about it it is a lot like a priority encoder.2) Separate it out into 3 separate tables one for Z, L1 and L2 and then do the simplification.

author: tiofilo75
author_rank: Contributor
timestamp: June 26, 2012, 04:25:25 am
content: I was able to figure it out. Thanks for the help everyone.
4 channel oscilloscope - Page 1
Forum section: electronics / beginners

author: clkaczor
author_rank: Contributor
timestamp: March 18, 2015, 06:28:16 pm
content: Which scope for learning on would someone consider a better oscilloscope 1104Z or SDS1204? Considering it for radio work, interested in getting into HAM radios and such. The SDS is 200 MHz with 2 Gs/s, would it be better for FFT? Does the Rigol still have too many firmware issues? I would have to pay for the 1104Z, because I would not hack anything it's kind of like stealing. So the prices are pretty close to each other. Does anyone even buy Siglent 1000 series scopes or the Waveace? Do Not see much info about them like the Rigol.Any advice would be appreciated.

author: katzohki
author_rank: Frequent Contributor
timestamp: March 18, 2015, 07:23:34 pm
content: The 1104Z is really good. Neither are really geared toward RF, but that shouldn't matter too much for starting out. You can get a lot done with just a scope.
4 Ohm, 8 ohm, 16 ohm 70V??!! - Page 1
Forum section: electronics / beginners

author: gooseEL34
author_rank: Regular Contributor
timestamp: June 26, 2014, 02:52:28 pm
content: Hey all-I recently scored an old Radio Shack 20w solid state PA amplifier. On the back, are screw terminals for the speaker load.There are 5 screw terminals on a strip labeled GRND, 4, 8, 16 and 70V.Can anyone tell me what the 70V tap is for? I have never seen that on an audio amplifier.ThanksTim

author: grumpydoc
author_rank: Super Contributor
timestamp: June 26, 2014, 02:59:11 pm
content: 70V (or 100V) lines were (are?) common in PA systems - you run audio at fairly high voltage around and then have a transformer at the loudspeaker to match whatever the 'speaker impedance and power is.

author: jlmoon
author_rank: Unknown
timestamp: June 26, 2014, 03:04:51 pm
content: Another way you can look at 70V line is like the multi KV transmission systems around your community. The line loss is much less when you step voltage up for transmission and then step down at "point of use" you obtain better power transmission with this technique. It is pretty hard to run long speaker lines without having voltage drop due to wire resistance which isn't good for the 4/8 or 16 ohm outputs on your amplifier.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 26, 2014, 03:07:51 pm
content: As grumpydoc said, audio is distributed at a high voltage (there were also 25V and 100V standards, but 70V is the most common).One important feature was that you could "tap" the speaker transformer for how much power you wanted for that speaker. See photo below.So you could set different speakers at different levels depending on the specific location, application, noise level, etc. etc.It also meant that you didn't have to juggle speaker impedances and rig up awkward series/parallel schemes to maintain 4 or 8 or 16 ohms, etc.

author: true
author_rank: Frequent Contributor
timestamp: July 03, 2014, 05:09:24 am
content: 70V is still extremely common in commercial audio. There are numerous reasons why:* When adding speakers one only has to take into account power consumed on the run; no special ohm load calculations or wiring* No special wiring - everything is in parallel* Speakers have taps so audio power (and thus gain) can be set lower in entranceways but higher in the main building* Less loss over distance (explained above)* Probably more I can't think ofI deal with 70V just as much as I do 4/8ohm systems. About the only time I'll find or use 4/8ohm systems in commercial applications is for small bars or restaurants where better sound quality is preferred or they're cheap and have some existing stuff.As for your Radio Shack amp? If you had to ask, you'll probably never use any terminals except GND and 4
4 Pin Ballast on 2 pin Lamp. - Page 1
Forum section: electronics / beginners

author: cart
author_rank: Contributor
timestamp: September 25, 2024, 08:12:45 pm
content: Hi everyoneI am having a very hard time finding Ballasts for a 13Watt UVC lamp.My lamp has 2 pins.My Ballast is a Harvard DKE 13 which has a 4 pin output of which one pair is Temperature Control.So I can not seem to get it to work on my lamp.Is it possible to run a 2 pin lamp from a 4 pin ballast?The reason I am asking is it is really hard to get ballasts for two pin lamps.Thanks

author: Zero999
author_rank: Super Contributor
timestamp: September 25, 2024, 09:24:55 pm
content: No, because it will use a high frequency inverter, which won't play nicely with starter and associated RFI suppression capacitor.The ballast doesn't have temperature control. It has a heater output to power the filaments at the ends of the tube.All you need is an inductive ballast.
4 Pin Fan Tachometer - Why 2 pulses per revolution? - Page 1
Forum section: electronics / beginners

author: bitshift
author_rank: Regular Contributor
timestamp: July 31, 2015, 07:14:34 am
content: Hi all,I've been playing with a 4 pin PWM controlled fan (Here's alinkto a specification for those interested).The tachometer output signal is defined to output two pulses per revolution of the fan. I understand that there are small magnets attached to either side of the fan. A pulse is generated each time a small magnet passes a hall effect sensor.Why are there two pulses per revolution and not just one?TL;DRIn a 4 pin fan why does the tachometer output two pulses per revolution and not just one?

author: dadler
author_rank: Unknown
timestamp: July 31, 2015, 07:24:40 am
content: Maybe this will help explain:http://electronics.stackexchange.com/questions/95301/what-exactly-is-the-purpose-of-a-hall-sensor-in-a-bldc

author: bitshift
author_rank: Regular Contributor
timestamp: July 31, 2015, 07:27:53 am
content: Quote from: dadler on July 31, 2015, 07:24:40 amPerfect, thank you
4 pin PCB right angle fan header - Page 1
Forum section: electronics / beginners

author: jshonw
author_rank: Contributor
timestamp: June 08, 2014, 09:47:40 pm
content: I am looking for PCB right angle headers that can accept 4 pin PC fans. The key tab is 3 pins wide and is offset to one side, so that it can accept 3 pin fans also. Do they exist and where can I get them?

author: fluxcapacitor
author_rank: Frequent Contributor
timestamp: June 09, 2014, 12:17:25 am
content: do you want thru hole or surface mount. This might do if you notch out the plastic,this one is thru hole.http://www.ebay.com/itm/10x-KF2510-4P-Connector-Kits-2-54mm-Pin-Header-Terminal-Housing-Right-Angle-/120992682503

author: jshonw
author_rank: Contributor
timestamp: June 09, 2014, 12:52:32 am
content: Trimming the tab as you suggested on a regular 4 pin might work for now, since I am only at the prototyping stage. Hopefully, I can find some proper ones, if this project ever goes into production.

author: peterszilagyi91
author_rank: Newbie
timestamp: April 16, 2018, 06:06:31 am
content: Have you find the right angle version for this connector?

author: palpurul
author_rank: Regular Contributor
timestamp: April 16, 2018, 06:14:47 am
content: I am sure you can find a suitable one from digikey.https://www.digikey.com/products/en/connectors-interconnects/rectangular-connectors-headers-male-pins/314
4 to 20 mA ADC Interface - Page 1
Forum section: electronics / beginners

author: Sikanda
author_rank: Newbie
timestamp: September 13, 2023, 07:28:25 pm
content: Hi,On the Texas Instruments website I found a video about designing a multi-channel 4-20 mA analogue input module. The analogue module uses a Delta Sigma ADC - ADSS114S08. The ADC has 12 input channels. The author discusses three different ways of making the 4-20 mA interface to the ADC. Unipolar operation, extended unipolar operation using diodes to obtain a voltage offset and bipolar operation using dual supply. The author chooses the last one.- Can you please look at the circuit below and tell me if I have done it as intended.- Will I get offset voltages in the measurement due to the common reference point for all analogue inputs?Videohttps://www.ti.com/video/5461116970001Datasheet - ADSS114S08https://www.ti.com/lit/ds/symlink/ads114s08.pdf

author: langwadt
author_rank: Super Contributor
timestamp: September 13, 2023, 07:34:43 pm
content: would make sense to move the TVS the other side of the PTC

author: Zero999
author_rank: Super Contributor
timestamp: September 13, 2023, 07:44:22 pm
content: Why use a non-standard value such as 4k? Why not 3k9 or 4k3? It won't make any difference. All those resistors do is limit the input current.

author: Sikanda
author_rank: Newbie
timestamp: September 14, 2023, 05:18:45 pm
content: Thank you for the hints. Anything else? Is that the way to go?
40 pin female header 2.54mm - Page 1
Forum section: electronics / beginners

author: ebclr
author_rank: Super Contributor
timestamp: June 04, 2016, 04:52:10 am
content: Is there a Technic to cut a 40 pin header to be 5 pin without destroying a lot of pins ?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: June 04, 2016, 04:58:28 am
content: You should only have to destroy 1 pin, yes? Cut with your flushcutters, trim off excess plastic, done.

author: sleemanj
author_rank: Super Contributor
timestamp: June 04, 2016, 07:52:16 am
content: Take your stanley (craft) knife, count out how many pins you want, score down the middle of the next pin after that (unavoidably deleted), snap, clean up the snapped ends.You want 5 pins, score down the middle of the 6th, snap, trim.I only score one side, one knife-score is all it takes to weaken it to snap at that spot.

author: Simon
author_rank: Unknown
timestamp: June 05, 2016, 05:00:29 pm
content: I just twist them and break them off where I want.

author: Watth
author_rank: Frequent Contributor
timestamp: June 05, 2016, 06:02:30 pm
content: I guess since these are headers, it's the female ones that are not supposed to be snapped apart. I guess, as said others, you could sacrifice one of the pin, and smooth the remaining part.

author: Simon
author_rank: Unknown
timestamp: June 05, 2016, 06:04:04 pm
content: oh, well yes you loose one receptacle, just cut through with cutter and file off as neccessary.

author: Ian.M
author_rank: Super Contributor
timestamp: June 05, 2016, 06:42:30 pm
content: Its easy if you don't care about the offcut, but if you need both pieces with only one pin's waste, it depends on the shell. If its glass filled hard plastic, you may have to use a fine-toothed junior hacksaw to notch each side of it as its hard and brittle enough that snipping it tends to damage the corner between the inter-contact separators and the sides. If its soft thermoplastic, surface scoring doesn't work too well and you may need to remove the contact insert so you can cut it without the cut being deflected.
4001 used as a NOR Set / Reset  gate pairing question - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 27, 2016, 02:18:19 pm
content: Hi, I am adding separate LED's to show just which trip function (loss of input signal at IC3 Pin6, high reflected power at IC1 Pin 13, and excess PA FET current from a Hall effect device looking at the end of the ferrite core of CH1), activated in the attached circuit. On a breadboard all works as expected with two 4001 IC's as Set / Reset Flip Flop NOR gates, and an HEF40569 used for inverting those signals that start High and go Low on fault.My question is, on the attached schematic, I am using either point X or Y to feed the Set pin of a 4001. When point X or Y goes higher the Q output of the 4001 goes High as expected, *EXCEPT* if I feed the reset pin from point X and am using a 10K or even 47K pull down resistor on the Set and reset pins. I have to remove any resistor on pin 1 to make it trigger on X going High. If I use Y as the input for pin 1 it works with a pull down resistor of 10K. I think I see what's occurring (the pull down resistor of 10K fed via a 47K resistor, and the 47K won't "overcome" the lower 10K resistance to ground), but am not sure.Effectively point Y is held to ground wherever the metering switch is set by a 100K resistor. Point X to ground by a 47K and 100K in series (147K). Does this mean I shouldn't use a pull down resistor on the 4001 input pin when connecting to either point?Obviously I am not showing the 4001 or connections on the schematic. Thanks for looking!

author: rstofer
author_rank: Super Contributor
timestamp: November 27, 2016, 03:50:04 pm
content: Draw out the signal flow to the flops and I'll bet you see a voltage divider where one resistor is pulling up and the other if pulling down. Do the math to determine the pin voltage and see if it is safely higher than the logic '1' threshold voltage.Or, measure the pin voltage with a DMM.

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 27, 2016, 04:06:44 pm
content: Quote from: rstofer on November 27, 2016, 03:50:04 pmGiven my inattention in maths classes and my age being somewhat too great to start afresh with mathematics, the DMM route sounds goodThanks for the reply!
400mv spikes on lm35 output when fan is running - Page 1
Forum section: electronics / beginners

author: lk
author_rank: Regular Contributor
timestamp: May 03, 2012, 02:47:48 pm
content: Greetings,Inspired by Daves, constant current source. I decided to build my own, and as the heatsink gets quite warm, i decided to have a temperature controlled fan on it, and that works well. Apart from those spikes that show up, i have a 0.1 uf on the output of the lm35. The 2n2222, that runs the fan, has its base driven by a 358 op amp.when the fan is not on there is no noise at all.I have a feeling that for this use i can ignore the problem, I'm just curious what could be done about such a problem.-lk

author: T4P
author_rank: Super Contributor
timestamp: May 03, 2012, 03:32:17 pm
content: Maybe the fan introduces spikes to the line ? (Or , unfiltered ground that is sent back to the pcb , might happen , who knows ?)Or EMI Interference from the fan ?

author: Unknown
author_rank: Unknown
timestamp: May 03, 2012, 04:58:12 pm
content: Are the spikes still there if you connect both the probe tip and the ground clip to ground? Does reducing the loop area of the ground lead or using a shorter ground lead change the shape/amplitude of the spikes? It may just be a common mode issue, or inductive coupling into the probe ground lead.

author: SeanB
author_rank: Super Contributor
timestamp: May 03, 2012, 08:19:56 pm
content: Put a capacitor of 100uF 25V directly across the fan power leads, and a series resistor of around 10R in the supply to the fan before the resistor. This will reduce the noise reflected back to the supply. Twist the leads of the fan together all the way to the control board Connect the heatsink to circuit common with a dedicated short wire, this should reduce it a lot.

author: lk
author_rank: Regular Contributor
timestamp: May 04, 2012, 03:41:01 am
content: Thanks everyone,I see the spikes if i probe the fan on its own, interesting, its a fan i pulled off a nvidia graphics card, so its behavior surprises me.Sean, you mean a resistor before the 100uF capacitor right?update: I just tested this and all those spikes are gone, so thanks a bunch.-lk

author: T4P
author_rank: Super Contributor
timestamp: May 04, 2012, 03:17:33 pm
content: Those fans are always as skinny as possible so most of the filtering is on the graphics mainboard itself.
40106 issue - Page 1
Forum section: electronics / beginners

author: biotron345
author_rank: Contributor
timestamp: June 07, 2016, 06:13:36 pm
content: Hi all,I was playing around with this today. I knew that pin 1 of the 40106 outputs a triangle wave with a much lower amplitude compared with the square wave from pin 2. I thought I could over come this by sending the triangle wave to an op amp and match it's amplitude to the square wave by choosing the right resistors. I realise there are other ways to achieve this but would this work?

author: danadak
author_rank: Super Contributor
timestamp: June 07, 2016, 06:33:47 pm
content: Did you forget to post schematic or picture of solution ?Regards, Dana.

author: biotron345
author_rank: Contributor
timestamp: June 07, 2016, 07:16:45 pm
content: DOH!!!!!!!!!!! Schematic up

author: Zero999
author_rank: Super Contributor
timestamp: June 07, 2016, 07:37:37 pm
content: The op-amp will amplify the DC offset as well as the signal so the output will clip. The LM741's output also can't reach anywhere near the rails so will not be able to produce the same amplitude as the CD40106, unless it's powered from a much higher power supply voltage.The normal Schmitt trigger oscillator produces a fairly poor sine wave. Why not add an integrator to make a proper triangle wave?

author: biotron345
author_rank: Contributor
timestamp: June 08, 2016, 06:57:07 am
content: Thanks Hero999...............more reading for me!

author: biotron345
author_rank: Contributor
timestamp: June 08, 2016, 03:21:49 pm
content: Hero999.........a little confused with the schematic you posted. Could you perhaps explain it? Thanks in advance!

author: Zero999
author_rank: Super Contributor
timestamp: June 08, 2016, 05:56:50 pm
content: Quote from: biotron345 on June 08, 2016, 03:21:49 pmThe circuit works on a similar principle as the previous one, except the RC circuit is replaced with an integrator.The op-amp is configured as an integrator which is inverting. The non-inverting input is connected to half the supply voltage, which could be done with a potential divider. Two of the Schmitt triggers are connected in series, making them non-inverting.Here's an alternative implementation of the circuit but it uses an op-amp configured as comparator for the Schmitt trigger. The advantage is it only uses one IC but it the disadvantage is it won't work at such a high frequency and the rise/fall time of the square wave will be longer.http://edudirectory.50webs.com/signal/SINGLE%20SUPPLY%20FUNCTION%20GENERATOR.htm

author: biotron345
author_rank: Contributor
timestamp: June 09, 2016, 06:32:19 am
content: Thanks, now it make sense!
4013 flip flop, which pins to ground? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: July 26, 2015, 12:44:13 am
content: I have built this circuit, and I am unsure which pins on IC4, a 4013 D type flip flop, should be grounded.Unused pins are 8, 9, 10, 11, 12 and 13. Should I ground 8, 9, 10 and 11?I don't know if just the unused data input pin should be grounded, or the unused clock and asynchronous input pins as well.Thanks.

author: Andy Watson
author_rank: Super Contributor
timestamp: July 26, 2015, 07:00:15 am
content: Yes, ground all unused inputs.

author: Chris Wilson
author_rank: Super Contributor
timestamp: July 26, 2015, 10:57:24 am
content: Thanks for the fast replies. Someone on another forum has also answered another query, when I powered the circuit up with just the 12V low voltage circuits connected, and I was about to switch on my sig gen to replicate a TX from my transceiver, I noticed a poor sine wave of low amplitude on my scope. I couldn't understand how it was showing an oscillating signal without the sig gen connected. Now I know the likely cause! The CMOS stuff has a very high input impedance and floating inputs are prone to self oscillateThe trip LED would also spontaneously come on after a minute or two of running with what appeared to be good square waves to the gates of the FET's. The FET's were not switching HV, in fact I have not assembled the RF side of the FET's yet. I am hoping this will also be cured by grounding the unused pins.Thanks for confirming which ones I need to ground!
4026 chip - counterpart for common anode displays  - Page 1
Forum section: electronics / beginners

author: Burczyk
author_rank: Contributor
timestamp: March 21, 2018, 03:04:12 pm
content: Hello.I am experimenting with 4000 series logic chips. I tested some johnson counters and divide-by-n counters. Now i wanted to test my 4026. But it turned out all my 7 segment displays are common-anode type. If i was to interface my IC with these displays i would have to use 14 transistors. Can someone point out a common anode 7 seg. display driver IC, that would be similar to the 4026?

author: fourtytwo42
author_rank: Super Contributor
timestamp: March 21, 2018, 04:25:41 pm
content: You could use a buffer chip such as the ULN2003 etc that will both invert your signals and provide the drive current you probably need anyway.

author: Chris-IP5
author_rank: Contributor
timestamp: March 21, 2018, 09:07:01 pm
content: I think the 4000 series expects common cathode 7-seg displays. I can't see any display driver IC in that series for common anode.My approach would have been to have separate counter and display ICs... but sadly not a solution for you if you only have common anode display.One of the other logic families might have a suitable display IC.

author: DC1MC
author_rank: Super Contributor
timestamp: March 21, 2018, 09:33:12 pm
content: Like 74LS47?

author: Chris-IP5
author_rank: Contributor
timestamp: March 21, 2018, 10:59:00 pm
content: Yes that will work with common anode display.Connect LT (pin 3) and RBI (pin 5) pins to +5V. Input pins 5V max of course.That is a BCD type so you need to provide a BCD input (4 wires).Is this helpful?

author: Burczyk
author_rank: Contributor
timestamp: March 23, 2018, 12:25:54 pm
content: Yes, thank you for all your replies.I managed to find a small common cathode display at the bottom of my parts box, i will use that for my experiments.
4060 Counter at Power UP - Page 1
Forum section: electronics / beginners

author: Del Tapparo
author_rank: Newbie
timestamp: December 11, 2012, 11:05:25 pm
content: Does anyone know if a 4060 counter will retain its count? i.e. When I power it up without a reset, will it continue counting from previous count?I wouldn't think so, yet I have a device that appears to work that way.

author: ivan747
author_rank: Super Contributor
timestamp: December 11, 2012, 11:59:27 pm
content: It shouldn't retain anything.Are you sure the voltage drops to 0 when you cut the power to your circuit?

author: Del Tapparo
author_rank: Newbie
timestamp: December 12, 2012, 12:16:15 am
content: Yes. The circuit only has the one chip (4060). It runs a motor for a specified period of time, stops for a delay period, reverses the motor, and repeats. The motor operates an arial tramway. The cars always stop at the station (end points), after proper setup of course. When you cut power, the tram stops anywhere between the ends. But when you power up, it always runs to the end point and stops properly. There are NO limit switches or any kind of position sensing. The only thing that makes sense to keep all of the timing in sync, is the 4060 retains the count.

author: ivan747
author_rank: Super Contributor
timestamp: December 12, 2012, 01:02:32 am
content: Perhaps the 4060 continues to receive power from a battery or large capacitor, therefore keeping its count.I don't like the idea of a tramway without feedback, sounds dangerous.

author: Del Tapparo
author_rank: Newbie
timestamp: December 12, 2012, 01:10:54 am
content: Power can be off for long periods of time (30 mins, 1 hour), and it still works. (The tram is a model)

author: ivan747
author_rank: Super Contributor
timestamp: December 12, 2012, 01:20:14 am
content: I don't know what else could else going on but I doubt the chip is retaining its count. Try to hook up a multimeter in parallel with the motor (autoranging off) and see if the motor still tries to run when the carts reach the end.

author: Del Tapparo
author_rank: Newbie
timestamp: December 12, 2012, 02:01:14 am
content: OK. I finally figured it out. I was trying to under stand the controller without actually setting up the whole system. The tram cars just hit an end stop and the motor keeps running. Nothing to do with the 4060. I knew the units motor kept running, but just assumed I had a bad one, because I didn't understand it. A friend just loaned me his, and it does the same thing.Sorry to waste your time. Thank you for the response.

author: Simon
author_rank: Unknown
timestamp: December 12, 2012, 07:13:06 am
content: Quote from: Del Tapparo on December 12, 2012, 02:01:14 amNo waste of time, you sorted it out didn't you ?
40A H bridge - Page 1
Forum section: electronics / beginners

author: wilmer
author_rank: Contributor
timestamp: October 24, 2024, 09:44:20 am
content: Hi, A long time ago I use to design PCBs, but I change fields. Now I am retaking the tools.An one of the first think that my son ask me was to modify his rideon with new motors. So as all dad with some tools knowledge I am overdoing it....... that it is what my wife said.The two motors that I will be using run at 12v and around 30A. The controller needs to interact with the original boards of the rideon as the radio and front buttons. I am planning to use a PIC as the brain. I have two questions: A) can you please critize the board? B) is my connection of the MCLR correct to program the MCU?I plan to use a pot to change the pwm proportionally.I will add a brake funtionality

author: elektryk
author_rank: Regular Contributor
timestamp: October 24, 2024, 10:01:32 am
content: I'd rather use driver IC and all N-FETs.

author: bborisov567
author_rank: Regular Contributor
timestamp: October 24, 2024, 10:19:20 am
content: I would add some snubber network to protect the mosfets from back EMF.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 24, 2024, 10:35:20 am
content: Quote from: bborisov567 on October 24, 2024, 10:19:20 amBullshit, freewheeling diodes are already there, additional snubbers would be for layout parasitics, not for motor BEMF.---Anyway, at that power level I'd seriously think about adding current sense (so you can terminate PWM cycles on overcurrent) and using integrated gate drivers (you could then use bootstrap types with all-NFET design).

author: wilmer
author_rank: Contributor
timestamp: October 24, 2024, 11:07:42 pm
content: Thanks, For the suggestionsDo you think that a bridge driver like the HIP4081AIPZ will do the trick?Thanks for the suggestion of the current sensor....as I am planning to share the design I think is a good idea... MCS1803 will do the trick.I will update the design with your comments and posted it again....
40xx tri state buffer chip? [SOLVED] - Page 1
Forum section: electronics / beginners

author: 5321488
author_rank: Contributor
timestamp: February 28, 2017, 05:36:18 am
content: **Solved**I am having trouble finding a CMOS 40xx series tri-state buffer chip so my first question to you is do they exist (in production)?And my second question: If there is not such a magical chip, i intend to make a tri-state buffer out of other logic as shown in the attached schematic. What would be the best rating and model of NMOS and PMOS transistors to use for the output stages, as shown?Thanks!

author: oPossum
author_rank: Super Contributor
timestamp: February 28, 2017, 05:47:09 am
content: CD4503

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: February 28, 2017, 06:18:28 am
content: Yep.Here at DK:http://www.digikey.ca/product-detail/en/texas-instruments/CD4503BE/296-2071-5-ND/67337They must still be in production if DK has 1400+ of them.

author: 5321488
author_rank: Contributor
timestamp: February 28, 2017, 06:26:45 am
content: Great! I must be blind...Thanks for your help