Low coefficient NTC resistors?

Started by Sylvia Else in sci.electronics.design12 months ago 42 replies

Anyone aware of such a thing? Clearly, one can achieve that just by putting a thermistor in series with an ordinary resistor, but my UPS...

Anyone aware of such a thing? Clearly, one can achieve that just by putting a thermistor in series with an ordinary resistor, but my UPS seems to contain a single component that behaves that way - perhaps less than 1% at 20 Celcius - it's in the circuit that controls the battery charging float voltage. Did they perhaps exist 20 years ago (when my UPS was made), for some reason? Sylv...


Carbon Pile

Started by OldGuy in sci.electronics.design9 years ago 12 replies

Who makes a good stable carbon pile? Stable as in it maintains its resistance as current is varied. 200 amp range, 100 VDC. Currently using a...

Who makes a good stable carbon pile? Stable as in it maintains its resistance as current is varied. 200 amp range, 100 VDC. Currently using a battery load tester but I want something I can mount on my own equipment. e.g. I have DC motor that I want to voltage up to see how it draws.


Is 3 Watts really too much to ask?

Started by Cursitor Doom in sci.electronics.design11 months ago 53 replies

Gentlemen, in pursuance of what is turning out to be a jinxed project (installing a dashcam) I'm attempting to drop 14.5V (the normal battery...

Gentlemen, in pursuance of what is turning out to be a jinxed project (installing a dashcam) I'm attempting to drop 14.5V (the normal battery voltage whilst the engine is running) to 5V for the camera. The camera draws at most 300mA so the regulator (an L7805CV) shouldn't find that task too much of a struggle, since it only has to disspate just under 3 Watts by my reckoning. I'd have ...


OT: Lead Acid Float Charger

Started by Jim Thompson in sci.electronics.design7 years ago 79 replies

I drive my pick-em-up truck every few months. So the battery is dead when I go to use it... like today :-( I'm looking for recommendations...

I drive my pick-em-up truck every few months. So the battery is dead when I go to use it... like today :-( I'm looking for recommendations for the _best_ (*) float charger I can buy to just plug the truck into when it's parked. (*) Cost no object. ...Jim Thompson -- | James E.Thompson | mens | | Analo...


Any low power low frequency quadrature receivers?

Started by Joerg in sci.electronics.design10 years ago 56 replies

While looking at a single sideband receiver project that may be coming up I checked the usual suspects for quadrature demodulators. Many...

While looking at a single sideband receiver project that may be coming up I checked the usual suspects for quadrature demodulators. Many won't (technically ...) go much below 100MHz. Some do and I need to be more in the 5-10MHz region. But they are massive guzzlers when it comes to draining the battery. Like this one which slurps a whole watt (!): http://cds.linear.com/docs/Datasheet/5584f....


Lead Acid puzzle

Started by Tabby in sci.electronics.design2 years ago 34 replies

Cart with 2x 12v 33Ah progolf AGM lead acids. 1.5 years after fitting new batteries the available range is down to below 10%. I'm not clear what's...

Cart with 2x 12v 33Ah progolf AGM lead acids. 1.5 years after fitting new batteries the available range is down to below 10%. I'm not clear what's gone wrong. The charger in use has been a cheap chinese one with 2x13.7v=27.4v output. Single stage charging only. It has always been promptly charged after use, and never run below 50% charge. I checked the battery voltages after charge, they wer...


oops

Started by Jan Panteltje in sci.electronics.design2 weeks ago

https://arstechnica.com/information-technology/2022/11/researchers-break-security-guarantees-of- tte-networking-used-in-spacecraft/ And will...

https://arstechnica.com/information-technology/2022/11/researchers-break-security-guarantees-of- tte-networking-used-in-spacecraft/ And will SLS even fly or just explode or crash? It Has To Fail! It almost has to fail, 16 years of development... Bad solder joints, burned out LM317, dead backup battery after 16 years... rotten electrolytics.. rust!


Li-ion UPS battery substitution in UPS

Started by Bert Hickman in sci.electronics.design1 month ago 53 replies

Does anyone have any experience swapping out old lead-acid batteries for Li-ion equivalents in a UPS? I see these batteries advertised as...

Does anyone have any experience swapping out old lead-acid batteries for Li-ion equivalents in a UPS? I see these batteries advertised as replacements, but I'm concerned about their safety in this application. New Li-ion UPS systems seem to be extremely expensive.


Alkaline battery reverses polatirity - cause?

Started by three_jeeps in sci.electronics.design3 years ago 7 replies

In my many years of dealing with electronics I've never seen this phenomena. I am curious as to a) the cause and b) the chemistry behind this. I...

In my many years of dealing with electronics I've never seen this phenomena. I am curious as to a) the cause and b) the chemistry behind this. I have a remote control that has four AAA alkaline batteries in series that power the remote control. For a period of time, before the remote became inoperable, the LED activity indicator would not illuminate when I pressed a key but the corr


How about it? Experiments of the third kind , take 999999.

Started by Jan Panteltje in sci.electronics.design11 years ago 59 replies

This is an idea for an experiment I may or may not do. The background: There have been reported seasonal variations in radioactive decay in the...

This is an idea for an experiment I may or may not do. The background: There have been reported seasonal variations in radioactive decay in the past. Now If I took a simple tritium light, and a good quality photo-diode, put both in a light proof box, and logged that with a 10 bit PIC ADC with a decent Vref for say a year to FLASH, say 1 sample / hour, run the whole thing of some battery. ...


TL431 replacement with 1.2V reference???

Started by mike in sci.electronics.design8 years ago 24 replies

I need an MP3 player that runs 24/7. All the ones I have shut down and switch to file transfer mode when you plug in USB. So, I think I need a...

I need an MP3 player that runs 24/7. All the ones I have shut down and switch to file transfer mode when you plug in USB. So, I think I need a 1.5V AAA battery eliminator. All my wall warts use a TL431 as regulator. If I could find a replacement with 1.2V-ish reference in TO-92 I could just drop it in and change one resistor to get 1.5V. What's a good cheap, shunt-regulator IC that wi...


Banning per minute EV charging fee.

Started by Anonymous in sci.electronics.design3 years ago 64 replies

https://ww.electrek.co/2019/12/24/california-bans-per-minute-billing-tesla-superchargers-will-ne ed-displays/ It's about "time" they realize...

https://ww.electrek.co/2019/12/24/california-bans-per-minute-billing-tesla-superchargers-will-ne ed-displays/ It's about "time" they realize that some chargers are EV highway robbery. As i posted some months ago, final charging (above 70% of battery cap) costs more than gasoline equivalent. At 90%, it's more like 3x gasoline equivalent.


Bulging Li-Ion power packs

Started by Tim Watts in sci.electronics.design3 years ago 10 replies

In the course of my work, today I was handed a defunct Apple Mac laptop. The person commented "BTW the battery is bulging a bit" Within 2...

In the course of my work, today I was handed a defunct Apple Mac laptop. The person commented "BTW the battery is bulging a bit" Within 2 hours I had 3 Mac LiIOn batteries with bulges. One so extreme that the casing fell apart in my hands. After a chat with the university fire officer, these are now in "secure containment" outside the building (a metal bin away from anything flammab...


poking rs232 port BMS

Started by legg in sci.electronics.design3 years ago 13 replies

I've got a battery management unit that is reluctant to demonstrate functionality. The vendor's terminal com software seems non-functional...

I've got a battery management unit that is reluctant to demonstrate functionality. The vendor's terminal com software seems non-functional (will not install). So far the only evidence of life is a control line (one of three) hard on, and rare /XFFE /FFF signalled outputs on the rs232 port. Internal DC-DC fails to power LEM sensor. Balancing terminals seem inactive. Can anyone recom...


Tesla Semi completes 500-mile journey weighing in at 81,000 pounds

Started by Fred Bloggs in sci.electronics.design6 hours ago 88 replies

These monsters have a 1,000 kWh battery pack. Of course they're not going to tell you it was doing only 25 MPH all the...

These monsters have a 1,000 kWh battery pack. Of course they're not going to tell you it was doing only 25 MPH all the way... https://www.teslarati.com/tesla-semi-81k-pounds-500-miles-range-elon-musk/


NiMh charging formula

Started by Andy K in sci.electronics.design8 years ago 22 replies

I have a "dumb" NiMh/NiCd charger. For 9 volt batteries, it specifies 25 milliamps. The charger manual gives this charge...

I have a "dumb" NiMh/NiCd charger. For 9 volt batteries, it specifies 25 milliamps. The charger manual gives this charge formula. Charging time(h) = 1.2 x battery capacity (mAh) -------------------- charging current (mA) 13.44 hrs. Is is formula useful or is there something better that factors in the starting Voltage ? Thanks.


recommend cheap and corrosion resistant electrical contact material

Started by mike daniels in sci.electronics.design2 years ago 12 replies

I'm looking for a low cost contact material that can withstand being exposed to unconditioned warehouse conditions for months without the surfaces...

I'm looking for a low cost contact material that can withstand being exposed to unconditioned warehouse conditions for months without the surfaces becoming corroded or oxides. The shape of these will be similar to D cell batteries with a spring on one side and a flat contact on the other. The device is not a battery but mounts similarly and must work reliable on first install. No jiggling ...


OT: Can CMOS battery on PC motherboard be hot-swapped?

Started by Joerg in sci.electronics.design10 years ago 74 replies

Folks, Got a Dell Vostro 200 mini tower with XP on there that seems to be a bit off in the realtime clock lately. Around five years old so...

Folks, Got a Dell Vostro 200 mini tower with XP on there that seems to be a bit off in the realtime clock lately. Around five years old so needs a new 3V coin cell on the mobo. In order not to lose all the setup stuff, can those CR2032 coin cells be hot-swapped while the PC is running? Of course using ESD straps, being careful and all that. -- Regards, Joerg http://www.analogco...


How to stop electrical whining noise?

Started by John Doe in sci.electronics.design4 years ago 40 replies

https://youtu.be/FSwZQtqWyHw Can that whining noise be easily eliminated? I am assuming its origin is easy for some to guess. It uses...

https://youtu.be/FSwZQtqWyHw Can that whining noise be easily eliminated? I am assuming its origin is easy for some to guess. It uses brushless motors controlled by an "electronic speed control" (ESC). There is a large cap across each ESC supply plus and minus. I tried adding a 1000 ?F low ESR capacitor on the battery input but that didn't help. Thanks.


Inverters vs wallwarts

Started by bob prohaska in sci.electronics.design5 months ago 55 replies

I'm setting up a UPS for my computer/comms equipment using an inverter/charger and battery from Amazon. The equipment draw is only about 40...

I'm setting up a UPS for my computer/comms equipment using an inverter/charger and battery from Amazon. The equipment draw is only about 40 watts measured with a Kill-A-Watt, but all the associated wallwarts use capacitive-input switching power supplies. That means they only draw current at line peaks. My seat-of-the-pants guess is that the duty cycle is around 10%, meaning that the aver...