Tagged Questions

0
votes
0answers
49 views

adjustable battery indicator

I've got a simple circuit powered by one 18650 LIon battery. Now i want to light up a LED when the battery voltage drops under a specified value (e.g. 3,4V) I know it would be easy with a ...
-3
votes
1answer
85 views

How do I measure ripple current in a battery charger? [closed]

Minimizing ripple voltage is major factor to avoid failure of equipment such as digital axle counters. (Eldyne) How do I measure ripple voltage in a battery charger with a 230 VAC input and a 24 VDC ...
1
vote
3answers
183 views

Convert 9v of battery into 5v at 3.5watt

I want to run Raspberry Pi using a general non-rechargeable 9v battery. Raspberry Pi needs 3.5W and 5V input. Questions: Which LDO should i use ? For what amount of time general 9V battery is able ...
1
vote
1answer
81 views

What types of batteries are typically used in UPS (uninterruptible power supply) and why?

They definitely need to be safe for indoor use so they can't vent, they should probably support deep cycling due to the nature of backup power supplies, and I imagine they should have relatively long ...
1
vote
2answers
133 views

How do I determine the maximum amp output of a battery pack?

How can I determine the maximum amp output of a battery pack? Some background: I've got a 5-AA battery pack hooked up to a microcontroller and some continuous rotation servos, but there's current ...
4
votes
1answer
127 views

Voltage regulation on the high side of a Darlington array?

I'm looking to build an 3.3V Arduino Pro Mini based LED driver that drives 3 (possibly 6) super bright 10mm LEDs (R, G and B). I intend to use this 3.7V LiPo battery and these LEDs. The LEDs have the ...
0
votes
1answer
85 views

Best and safest supply for 12 standard servos or more?

I am building an hexapod 2DOF robot, and I had planned a Power supply (5V/5A) for all devices, like this : Would that work and be safe? I have another plan , to seperate the power between servos ...
1
vote
1answer
121 views

Getting a higher voltage from a battery than specified

This may be a totally stupid question, but say I have a battery that supplies power at 7.5 V. Is there any way to boost its voltage to provide 9 V? I know you can step down voltages in many ways ...
1
vote
2answers
108 views

How to connect a DC socket to a switch

I have a basic flip switch that I want to use to control whether a DC power socket is providing energy (from a connected battery pack). The power socket has three prongs, the switch has three, and ...
1
vote
1answer
65 views

Possible to determine a device's power requirements based on the batteries it takes?

I have a magnifying glass LED lamp that I lost the power adapter to. There are no power requirement markings anywhere on the device, nor do I have the box/manual. Short of trying to find the ...
-1
votes
1answer
737 views

Battery powered portable wall outlet?

For a college competition we aren't given any wall outlets to power our devices. We are purchasing (we don't have it yet) the wireless camera kit in the following link and we need to rig up a portable ...
2
votes
2answers
355 views

Can we connect battery negative terminal to oscilloscope ground?

I want to test my setup with 200Ah battery and check the outputs on oscilloscope. While testing can I connect battery ground to the oscilloscope ground? Is there any safety risk, as oscilloscope ...
2
votes
2answers
142 views

What is the proper name or part number of a 12V DC female car adapter with leads?

I've searched hobby sites like SparkFun, Digikey, BGMicro, and Jameco. I'm starting to wonder if I'm calling this item by the wrong name. What I'm looking for, exactly, is a 12V female car adapter ...
2
votes
1answer
76 views

Why is it only one of four batteries (Li Ion) is drained?

I have a programmable TV remote control ( a Marantz I've had since 1999 or longer if it matters), it uses 4 AA batteries. I often find (at least when I use Li-Ion, non-rechargeables) that when the ...
4
votes
1answer
127 views

How to protect an electronic construction kit (a toy) from damages?

As I child, I had this electronic construction kit called Elektronik 1. It was manufectured in former Czechoslovakia, based on resistors, diodes, bjt transistors, capacitors, an LW+SW radio antenna ...
4
votes
1answer
320 views

Arduino and Backup Battery Power

I have a very simple project that is working off of an external "wall wart" power supply and I would like to add a back up battery in case of power failure. I have breadboarded a backup power supply ...
4
votes
1answer
115 views

Tapping the battery from an UPS to feed low voltage devices

My UPS powers one 120V AC device and a whole bunch of small 'bricks' that end up rectifying things down to 5-12V DC. Instead of using the 'bricks', my idea is to tap the battery directly, and use ...
1
vote
2answers
441 views

Common ground between battery and AC/DC adapter

Is it possible to connect an AC/DC power adapter's ground (-) to a battery's negative side? I am powering a car radio with a 12V AC adapter. That works fine. However, if the radio loses power, it ...
2
votes
2answers
108 views

Need chargeable momentary 15 watt regulated voltage source

I'm working on a RF telemetry side-project that requires an amplifier IC to be run for about 5 seconds bursts between charges. The system is portable and runs off of a 3.3V battery that can supply ...
17
votes
2answers
1k views

How is wristwatch with 10 years battery life possible?

Turns out Casio offers a handful of wristwatches with "10 year battery life". The claim is that thanks to "an advanced technology" the battery life in those watches is extended to ten years. Now if ...
3
votes
1answer
220 views

Battery in parallel with main power source

I have a system that is powered by a main voltage supply and I want to connect it to a battery for backup, in case of power outage. I need to know what would happen if I connect the system with the ...
2
votes
2answers
194 views

How to best estimate power consumption for a system?

I'm not an engineer, I'm a software guy getting into hardware - so bear with my ignorance! I'm in the process of building a system with many components (e.g. a computer, many sensors, a few motors, a ...
-1
votes
1answer
91 views

Good battery back for home computer (e.g. iMac, PC) in case of power cut [closed]

I am wondering it there is anything in commerce such as a battery pack for home computer (e.g. iMac, PC) to connect between the computer and the electricity cut and safeguard the computer from any ...
6
votes
4answers
1k views

Least expensive way to plug in a microcontroller into 120V (without wall wart or batteries)

I need to be able to power a Atmega168 by plugging it into a wall. The circuit is a little bit more complex but not too much. The Atmega168 needs between 1.8V and 5V at 200mA. The ideal solution ...
3
votes
2answers
639 views

Charging affects battery life?

I wish to understand how a battery charger may best be designed in order to maximise the life of Lithium Ion batteries. I have specified Lithium Ion batteries as they are what is used in most laptops ...
4
votes
2answers
868 views

How to lay out a schematic for review? Please critique

So, because I haven't posted a schematic for review before, I have no idea how to do it. Apparently, my previous attempt was poor. I got some actionable feedback, but I'm looking for more! I would be ...
2
votes
2answers
103 views

Device is reset when switching power sources

I use a home weather station. It is powered by two AA batteries (2 x 1.5 = 3.0 V nominal). The problem is that it eats more than 1 mA and that is quite a lot of power and I must buy a new pair of AA ...
3
votes
1answer
1k views

Can I recharge batteries with a normal AC to DC transformer? [duplicate]

Possible Duplicate: Charging 3 AAs in series My batteries charger is not working, but I have an AC to DC transformer that can output different voltages. If I connect two 1.5v ...
3
votes
1answer
171 views

Can a majority of DC electronics run on high current (i.e. lamp, car) batteries directly?

I've seen some people run an inverter off a large set of batteries, to power mobile devices and whatnot or even game consoles. My thoughts are, if I can rig some lamp batteries together and use a ...
5
votes
2answers
527 views

Can 12V Batteries be made to act as a ±12V power source?

I am an undergraduate electrical engineering student, and as a final project for one of my classes I made a speaker system which could play music connected through a 3mm cable. The system was powered ...
2
votes
1answer
129 views

Spec'ing power supply to replace a battery pack in a DIY project?

I am attempting a DIY hack that involves (among other tweaks) replacing a battery pack with a PoE power supply. The battery pack in question uses 8 1.5v D-cells in a series-parallel configuration that ...
2
votes
3answers
271 views

Charging 3 AAs in series

I'm currently repairing a project built by someone else and want to avoid tinkering with it as much as possible. I am looking to recharge 3 AA NiMH batteries (at 1.2v each), that are in series. I ...
3
votes
3answers
395 views

Deciding between 7.4V and 11.1V power

Suppose I had a unit that could accept DC power between 6 and 14 volts, and the choice of using either a 7.4V 1000 mAh or 11.1V 1000 mAh battery. Do either of these choices offer a clear advantage? ...
2
votes
2answers
967 views

Solar power egg incubator

I'm going to Africa this summer for a veterinary mission and need an egg incubator. Considering I will not have a steady supply of power I need to find an efficient way to power an incubator ...
18
votes
4answers
2k views

When a battery is your power source, what is ground?

For the sake of not incorrectly connecting my power supply and damaging my board I'm going to ask a relatively dumb question. Is ground on my board the negative terminal on my battery? Explicitly ...
5
votes
3answers
3k views

Powering laptop from 12V sources without inverter

This question has two parts: 1) How inefficient is it to boost 12V to 120V and then back to 12V as in using a traditional car power inverter to power a laptop (i.e. the 12V car battery power is ...
0
votes
5answers
262 views

What's the name of the device I'm looking for

I'm looking for a device which monitors a 3.3V line. When the line drops below, say, 2.7V, I would like it to switch power over to a battery backup (3V lithium coin cell.) It would also be good if it ...
1
vote
3answers
686 views

Ipad charging via usb port

Ipad doesn't charge while in use and connected to the usb port. It definitely charges when connected to the supplied 10 watt power adapter. The USB port, as far as I know, supplies 5 watts. Can we ...
8
votes
4answers
810 views

What are the basics of making a rechargeable battery pack?

We have a device that runs off of a AC adapter, or a pack of 8 AA batteries. Since in normal use we use both, it would seem to make sense to have the battery pack recharge while using the AC adapter - ...
5
votes
7answers
2k views

Dummy battery shells

I have a device that takes two AA batteries and I want to replace it with my own external power source and regulation circuitry. Instead of clipping or soldering wires to the device contacts, I would ...
5
votes
3answers
1k views

How do I design a device to automatically switch to the backup battery?

I've been told that many kinds of batteries work best if they are used until they are completely drained, and then recharged. (Edit: The "memory effect myth" is quite widespread. Batteries work just ...