How to change 3v to 2v?

I want to install some LED string lights in my garden. The package comes with a solar charger (2V 100mA), built in battery (600mAh) and 30 meters of wire and 300 LED bulbs. The problem is that I cannot use the solar charger this time of year. So I want to cut the wires and join them to a power supply. The lowest voltage adapter i can find is 3V. Do I need to change the 3V to 2V? How?

Question by MartinaA5 2 years ago  |  last reply 2 years ago

can i fix a laptop battery with these? Answered

I have a powerbook 190 battery, but the batteries are all corroded and have leaked some acid. i was looking online, and i found some batteries, but i don't know the mah value of the original batteries, so i think these ones will work. it originally has 12 batteries in the pb190, so i'll be needing to get 12 of these. they will work, right?

Question by zack247 8 years ago  |  last reply 8 years ago

Running LED on 1.2V rail

I have a board I am working on, and 3 voltages i'm working with: 3.3V, 2.5V, 1.2V. I want to have "Power OK" LEDs for each voltage rail. A look on digikey shows me that 3.3V and 2.5V wont be a problem, but there are no LEDs with a voltage drop less than 1.2V... and if there is, theyre probably expensive. So what is a simple way to have a "Power OK" led for 1.2V rail? p.s. I'm using all 0603/surface mount stuff.

Topic by samurai1200 9 years ago  |  last reply 9 years ago

Electric scooter?

Has anybody made a electric scooter that is ran off of a drill motor that takes 7.2v?????

Question by TSC 8 years ago  |  last reply 8 years ago

how to use a simple 2V LED in High voltage circuit? Answered

Hi! I have 100V 0,5A DC circuit and a simple  2V 0,02A LED, what shall I do if I want the LED to shine but not to burn it. Thanks!

Question by IgorsS 3 years ago  |  last reply 3 years ago

I need a circuit to reduce 11.1v Lipo battery to 2v?

Preference is to use a voltage regulator to get a constant voltage output. If it can have a LED in the circuit somewhere along the way to indicate when it is connected. Kind of know what I need but not enough to put a circuit together.....anyone help?

Question by Have-a-go 4 years ago  |  last reply 4 years ago

A 3.2-3.6 green forward voltage LED , uses 2 ma. to operate? What amperage can it safely handle?

I would like to use one as a charge indicator for a 2500ma. rechargeable AA battery connected to a 2v., 600ma. (full sun) solar panel.2v. solar + 1.2v charged AA battery = 3.2+ v. and should turn the LED on, but can it handle the amps. or does it need a resister in the curcuit to protect it?

Question by heyfeaver 9 years ago  |  last reply 9 years ago

2 Different LEDs on One Circuit?

If I have a Red Led that takes 2v and a green led that takes 3.2 volts...then can i use 5.2 volts to power them?? Will that work without giving too much juice to the Red LED?? THANKS!

Topic by Joe426 11 years ago  |  last reply 11 years ago

How can I reduce the output voltage of a zener diode?

Hello, My main goal here is to get an LED to light up when it "detects" over 30V, regardless of the specific output of the voltage source. I attached here an image of the circuit that I currently have. The output of the zener diode is about 30V. What I want to do now is reduce this output to 2V in order to light up an LED that has a 1.8-2.2 VDC forward drop and a max current of 20mA.  I was thinking of attaching a voltage divider to this circuit in order to lower the 30V to 2V, but I'm not sure how, especially with the zener diode involved. Can anyone help me?

Question by frossiove 6 years ago  |  last reply 6 years ago

Sound activated switch

Hey, my friend is a drummer and he's trying to install LEDs inside each one of his toms that would come on when he hits the tom. He doesn't know anything about electronics so he asked me and I don't know much either so I'm asking all you awesome people at Instructables. What I want is a simple sircuit that will not cost me above £5 that will allow me to do what I mentioned above. I have a soldering iron and can solder stuff easily so I just need the parts and (preferably a stripboard) layout. He will be using a max of 16 red 2v 20mA LEDs in each tom so the circuit will have to be able to supply either approx. 32v 20mA if in series, or 2v 320mA if in pararell. So, any recommendations?

Topic by kacper00100 8 years ago  |  last reply 8 years ago

Running LEDs?

Quick question, really. Anyone know if it's possible to run LEDs in series straight off of wall current?  For instance, lets say I have 60 2v LEDs connected in series. Could I just put 120 VAC into them (with the proper resistor of course) and they'd light up with no problem?

Question by tylervitale 7 years ago  |  last reply 7 years ago

help making solar charger please read?

I want to do many things in life, one of them being able to harness the sun..., anyways, hi all, im interested in making an iphone charger such as this one now i dont really want to spend much money on this (he says i need about 70 bucks) i have about for good panels that say i should get 2v at 20amps but i get more than 2v, i have 2 diodes i got from radioshack so i think im covered there, any ideas or thoughts on how to do this would be great, also i want to learn the formula for calculating what ratio of amps and volts i need to charge a battery thanks all

Question by tylak 9 years ago  |  last reply 9 years ago

Transistor Voltage Inverter?

I am a newbie and was hoping someone could assist me. Given the following schematic which takes a voltage of 12v and considers it off and a voltage of 2 volts and considers it on can someone tell me what changes would need to take place regarding capacitors and resistors (if any) to account for 20v instead of 12v? Meaning that when 20v is considered off and 2v is considered on.

Question by TimothyE2 3 years ago  |  last reply 3 years ago

Transistor Voltage Inverter

I am a newbie and was hoping someone could assist me. Given the following schematic which takes a voltage of 12v and considers it off and a voltage of 2 volts and considers it on can someone tell me what changes would need to take place regarding capacitors and resistors (if any) to account for 20v instead of 12v? Meaning that when 20v is considered off and 2v is considered on.

Topic by TimothyE2 3 years ago  |  last reply 3 years ago

are these sufficient specs for a multimeter?

These are the specs off a multimeter im about to buy. are these enough to do electronic projects off, fixing electronics, and etc? if not then what do i need then? thanks DC Voltage: 200mV-1000V AC Voltage: 2V-700V Temperature: 20°-1000°C Resistance: 200Ω-20MΩ DC Current: 2mA-20A AC Current: 20mA-200mA Capacitance: 2nF-20µF Frequency: 10Hz-20kHz  

Topic by leader1 9 years ago  |  last reply 9 years ago

LED power consumption question. Answered

I need to power 62 LEDs in series. Does this mean I also need 62 1K resistors? And if I do, does that mean I need a 248V power supply?! Isn't each LED a 2V power consumption as well as each resistor? That math doesn't seem to add up at all, any help (and lessons in powering LEDs) is greatly appreciated. Thank you for the help!

Question by Schmidtn 9 years ago  |  last reply 3 years ago

Christmas lights aren't working :(

I have a small set of Christmas lights that will not come on. With my multimeter I tested the fuses, several light sockets (the one closest to the plug, the one furthest away, and one closer to the middle), and the female plug on the end. I'm getting 120v coming out of the female plug, the sockets are providing between 2v and 4v, and the fuses provide almost no resistance, and the filaments are visibly intact. What's wrong?

Question by C18H21NO4 9 years ago  |  last reply 9 years ago

LED car lighting problem!

I put some LED's in car, connected them to door sensors, but ~2V still flowing trough when door is closed (I think because sensors are grounded to frame) and LED's stay barely lit. So I need something to stop current. What would be my best option?

Question by KozisKey 8 years ago  |  last reply 8 years ago

Converting a 12V Lead acid to a hydrogen generator? Answered

Is it possible to take a 12V lead acid battery, remove the acid from all 6 cells and replace with water and connect to a 12V power source, and get H2 and O2 gasses bubbling out the top? The reasoning behind this question is that the 12 volt lead acid batteries are made of 6 cells, each producing about 2 volts, connected in series.  If instead of producing 12V we could (by removing the acid and replacing with salt water) feed it 12V, wouldn't we have 6 hydrolysis cells running at 2V each?   6 cells of 2V hydrolysis cells is nothing new, but has anyone of you ever tried to convert a lead acid battery before? Is the lead going to be any good as electrodes? Will the lead oxidize too fast? Will the there be any chemical reaction that would change the produced gasses? Should I be worried about lead poisoning for even typing these words? Should I be asking anything else I haven't thought about? Thanks!

Question by Morgantao 5 years ago  |  last reply 9 months ago

I am making a blue laser pointer can i use this diode with this module?

Diode- module- Iwill run the laser at 100 millawatts.

Question by DELETED_cdousley 9 years ago  |  last reply 9 years ago

Sloar powered fans with battery charger.?

I am looking for a solution to a small problem I have a solar powered fan details are Current: (isC) 300mA Output: 2V Motor-current: 20mA to 100mA Motor-voltage: 1V to 3V I would like to have a solar panel charging the batteries & running the fan during sunny daylight hours & double AA or triple AAA bateries running it after dark. Any easy solution please. Thanks

Question by Oslove 9 years ago  |  last reply 9 years ago

Boost Converter?

I make the rwilsford07 boost converter, but it doesnt work. The mosfet start heating and only gives 2v. I check the oscilator and is working perfectly, I try diferent things butit doesnt work. Before I make 120v, but I dont know how it stop working, I nad rebuild the circuit like three times but nothing happens. Can you help know why is this happen?

Question by Kurt Gerhard 7 years ago  |  last reply 7 years ago

Dropping 1v?

I'm designing a circuit for a very high precision installation, and I need to regulate a 6VDC supply to 5VDC. I have looked at various regulators, but most seem to require at least 2v above the output. It also needs to be very precise, available in a 500mA package, and have a very low current draw. The less external components required, the better. Voltage dividers won't work as the battery will vary in voltage from full to empty.

Question by andy70707 7 years ago

Basic Op Amp question

Hello, If the input to the positive terminal of an op amp is 12V, the input to the negative terminal is 10V, and there is no supply voltage, the output voltage is 2V and the output current is 0. Correct? Now, what I don't understand is what happens to the output voltage and current if I connect a supply voltage of, for example, 15V. I know that the output voltage and current both increase, but I don't know the math behind it. Can someone explain this to me, please? 

Question by frossiove 6 years ago  |  last reply 6 years ago

Buck Converter for Parallel LED's

So I am trying to make a gift for someone that will include about 100 LEDs. These LEDs have a forward voltage of 1.8-2.2 ( I am going with 2V) and a max continuous forward current of 30mA. The LEDs:;=item2a16538fe0 Now, I want to be able to plug this sign into a wall so I have purchased an AC to DC power adapter that plugs in into a standard 120V AC outlet and supplies 12V with 2A of current. Here it is: I know one way I could make this work is to have multiple series of 6 LEDs, as 6 LEDs in a series would then require 12V. However, it would make this project a LOT easier to have all the LEDs in a parallel circuit, so I can connect one whole side to the positive terminal and one whole side to the negative terminal. I wanted to know if I could do this: Plug the two wires (+ and -) going from the AC to DC adaptor into a Buck Converter set to 2V and wire it to all the LED's via one wire to a bus wire connected to all of the LEDs' negative terminals and same for the positive terminals.  The converter I was looking at:;=item4ad24add60 Also, if I place the switch in between the AC to DC power adapter and the buck converter, the converter would only be on when the LED's are on, right? Lastly, would all the LEDs have the same brightness? I know at 2V with 100 LEDs the output would need to be about 3A. Is it okay given that the power adapter supplies 2A but at a higher voltage? As in does the converter convert the electricity to a lower voltage but a higher current?

Topic by soulmouse 5 years ago  |  last reply 5 years ago

LED that light up if the battery is charged

I am making a solar charger for one Ni-Mh battery 3000ma. My solar cell is 2V 300ma. I want there to be an LED that will light up, if the battery is fully charged, I went through alot of articles online, and here is a circuit that I think might work, but I'm not sure, so if you could tell if this is going to work or not, it would be great, and any modifications I can do. I'm not sure about the value of the diode. 

Question by NiKiToS 7 years ago  |  last reply 2 years ago

What can i power with a small wind turbine?

I have recently built a small wind turbine for fun and now im looking for something i can do with it. The original idea was to charge 12v batteries to run an inverter but i got a shock that in a normal breeze, the turbine can only generate between 1.2v {normal breeze} to 2.5-3v{ gusty winds} So what usefull thing can i do with a turbine that makes 2v?

Question by microbike 7 years ago  |  last reply 7 years ago

the OUTPUT voltage of an mp3 phone jack?

I want to build a vu meter using the lm3914 now it it voltage coming to it is equal to 1.7v all the led with work so i need to devise that on 10 to know the lowest voltage to, turn on the first led. that's the clear part now i don't have an oscilloscope in my home so i cant know the out put of my Samsung galaxy ace4 / i want to know the out put so i can build an amplifier wish amplified the signal to  around 2v

Question by TN_inventor 2 years ago  |  last reply 2 years ago

Is it possible add mA to solar cells in series/parallel circut if you don't use the same number of cells in each circut?

I had in mind 3 circuts running in parallel with one at 4x2v(8v total at peak), and two other circuts running only one cell each, 2v. The mA of each single cell is at 40mA. Would this circut setup make it 120mA? It would be nice to solar power my airsoft rifle's 6xAA 600mAh(3000mAh total) battery pack in less than 30 hours with only a diode in the circut...

Question by ethereal haze 10 years ago  |  last reply 10 years ago

Help! (5V psu problems)

Help!I'm trying to make a 5V psu for programming my new (but not so shiny v_v) ATtiny2313'sI've got the circuit shown below set up, but I'm getting out around 5.6V, when the spec sheets say that I'm supposed to be getting out 5V (+/- .2V) I'm using the LM 340t5, just 'cause I don't have any other regs (except for the MC78M05CT, which is basically the same thing.Any Ideas?!EDITI know what was wrong - it was my meter, it really was 5V all along ;)

Topic by T3h_Muffinator 11 years ago  |  last reply 11 years ago

How to drop from 12vdc to 2vdc?

How to drop from 12vdc to 2vdc?  I have some 12volt rocker switches that I have bought for my boat livewell pumps. They have a led light that is supposed to go on when I turn the switch but it doesn't. It says I needs DC 2V 10mA-20mA for LED Light to work. The switch works ok with the pumps, I just would like to have the led on when it operates. How do I drop from 12vdc to 2vdc so I can bring power to the leds? Thanks to all. Lion_Heart

Question by Lion_Heart 8 years ago  |  last reply 8 years ago

Laptop Fan voltage booster

Hi, my laptop is overheating because the fan isnt fast enough. My idea is to build a small voltage booster to increase the fan voltage a small bit. It will be overvolting the 5v fan but i dont mind. For example, when idleing, fan voltage is at 3.5v and at full load its at 5v and i would like it to be 1-2v higher at both points WHILE still maintaining the variable control (spinning faster and slower as needed) Problem is, im pretty good at soldering but i dont know how to make one. Could anyone help with this project Thanks

Topic by ttg tricksh0tzz 4 years ago  |  last reply 4 years ago

Would a solar panel with more amps/lower voltage charge 4AA batteries faster or slower than more volts/fewer amps? Answered

I'm trying to make a solar powered battery charger for my 4AA rechargeables, and I'm stumped on what kind of solar panel I should use. I have two solar panels: one 0.5V 800ma, the other 2V 200ma. Which solar cell would be better for what I'm going to be using them for? And I'm wondering what the specs of those solar garden lights are, and if the solar panel for the garden lights is strong enough to charge the batteries.

Question by Justin Lam 9 years ago  |  last reply 6 years ago

A couple of servo related questions.

I was thinking of doing some sort of robotics for the upcoming microcontroller contest, and need to reduce the weight of my design. So, try and lighten the battery pack, and give more current, I want to use 2XAAA @ 3V, instead of regulating a 9V cell down to 5V. The PIC supposedly will run on 2V. So the question is, how well will a servo perform on 2.5 to 3.0V, and what will the current draw be with a light load (I have heard that they can draw a couple of amps with a very heavy load).  Also, I have some 4V lithium ion cells out of a laptop, and need to charge them (They last so long on one charge, that I have not had to charge them since removing them from the laptop).

Topic by The Skinnerz 8 years ago

How to power a High power laser diode?

If I build a 42A Constant Current PSU which can supply 1.2-6v, will the laser diode only draw 1.8-2V or will it try to draw to much voltage and damage its self? I have a 40W CCP CW Laser diode, here are some characteristics. Operating Voltage (V) <2.0 (1.8 typ.) Operating Current (A) <46 (42 typ.) I know that laser diodes will try to draw as much current as possible and suffer thermal runaway, so they need constant current power supply's. If anyone has any information on how to power high power laser diodes please let me know. All help will be greatly appreciated! 

Question by deltawars 4 years ago  |  last reply 4 years ago

Problem constructing a solar powered waterfall, please help? Answered

Hello, I have constructed a waterfall in my garden. It consists of a small dc pump which consumes 0.35a at 12v and a bigger pump which consumes 0.87a at 12v and a 5050smd led strip encased in a tube to make it waterproof, which consumes 3.7a at 12v totally 4.9a at 12v. I have a solar panel with 12v 30w and a solar charge controller with 12v 6 a capacity and a sla battery 2v 7ah capacity. I calculated a runtime of 1.4 hours when all three devices are connected together. But they last for only 30 seconds and then the charge controlled shuts them down with low battery indicator. I don't know what went wrong, can someone please help?

Question by himtec 6 years ago  |  last reply 6 years ago

Will this circuit work to make a solar powered USB charger? Answered

Would this work? It's supposed to charge both the batteries and whatever is in the USB, and then when there is no light the batteries will charge the USB. IN914 is to prevent battery discharge, LM7805 is to change voltage to 5V. The question mark is for a a resistor i heard you need to bridge the white and green connections so it works on iphones/itouches. Anyone know which it is? Link to better image of circuit: Using this solar panel:;=44&products;_id=262 EDIT: I realized that I need two solar panels in series to get 12V, because 6V won't be enough because the LM7805 takes 2V. Am I right? In that case, wouldn't it make more sense to put the batteries in series with the USB

Question by FireFreek 8 years ago  |  last reply 8 years ago

How to get my portable charger working?

Im building a portable USB charger but for some reason my phone ins't showing any sign of the charger being connected. It used to show when it was connected but I cant figure why it isn't now. I measured the voltage going to the USB its 5v and the two data lines are 3v. I used 33k and 22k for the data lines so i can get 2v to each line. Is there anyway someone could kinda assist me on making this circuit on a breadboard i'm kinda getting confused on how to set it up. Also is my 7805 going bad because sometimes the input voltage is the output voltage.

Question by lsavage-1 6 years ago  |  last reply 6 years ago

RC car batteries 7.2v to higher voltage?

Hi, its me again and i was wondering if you guys could help me. Well i just got this ( electric off road truck and this monster is insanely fast. But i want a bigger battery. In the instructions, it says the trucks input is 7.2 volts up to 16 volts. But thats the problem, my dad and I are skeptical about putting a battery over 7.2 volts in there. I am hoping to get an 8.4 volt battery (;=2) like this 7 cell one but am still skeptical about even this 1.2 volt jump. Can anybody tell me if anything  will fry, or be perfectly fine.

Question by Thelonelysandwitch 9 years ago  |  last reply 1 year ago

Why is my step up converter not increasing voltage and why output is a little lower than input?

My step up converter is not working ,it wont increase the voltage . I used a multi meter and the output ends up being lower than the input like for example when I connected the battery to it, the battery was at 8.40v and I checked the output and it was 8.10v . I was trying to make a DIY speaker for the first time,  I am new to this.  step up converter  is called a MT3608 LM2577. I got it off of aliexpress. The battery i used is off a battery pack .it is 8200 mah and 9v

Question by Alex345 2 years ago  |  last reply 2 months ago

Li-ion vs Li-poly battery? Answered

I m currently searching for a battery that has an high discharge rate and I found these two:   Li-ion:;=item2a1a7a8482 Li poly:;=item53f020cfc1 I need 40 volts so If I buy the Li-ion y will buy 4, and 2 of the Li-poly. I want to know which battery will be better for an high discharge for about 3 seconds, and about 15 times. I will use the batteries to create an high powered electromagnet to move steel. Thanks

Question by Kurt Gerhard 6 years ago  |  last reply 6 years ago

How to add 2nd battery to circuit or increase voltage

I have a Normally Closed NPN inductive proximity sensor which operates at 10V. I use it to control a load (light bulb), which is normally on, and goes off when the proximity sensor detects metal. The problem is that I need to work with portable batteries, or something like an acid battery, and ideally not exceed 12V for safety reasons. Since the sensor needs 10V to operate, this only leaves me with 2V for the light bulb. I need to increase the voltage to the light bulb so that I can use a decent light source. Is there a way of adding a 2nd battery to the circuit so that the bulb has its own power source, yet that too is controlled by the sensor (otherwise the bulb would just stay on continuously). Any other solution would also be appreciated. Current circuit diagram attached. Thank you.

Topic by nathanimate 3 years ago  |  last reply 3 years ago

Any objections to my battery charging solution? Answered

I bought some cheap 360 battery packs on the internet and big surprise they don't work.  The problem is that the built in charging circuit charges the packs to around 2.26v when my controller wont turn on until closer to 2.5v.  My idea is to use the indicating LED (that came as part of the pack) that has a forward voltage of around 2v to drop the 5v charging voltage down to 3v and charge the packs to that voltage.  Theoretically when the packs reach 3v the LED will not be able to sustain the forward voltage and will turn off stopping current flow to the batteries and thus stop charging.  I have a lot of knowledge about electronics, however my knowledge of batteries and their sensitivities is just about nill so I thought I'd ask here before I rig this together and get an idea of the likelihood of the batteries blowing up.  I've attached an image of the proposed circuit any knowledge would be greatly appreciated.

Question by double_g 6 years ago  |  last reply 6 years ago

RC Toy Car Battery Upgrade and More

Hi,I am new to the world of electronics...The other day, I planned to upgrade the lighting in my RC car.My RC car runs on 4 x 1.2 V 2800 mAh rechargeable cells. The circuit includes 2 motors (Motor 1 for moving the car and Motor 2 for changing the direction). It also has 2 front lights, which glow when the car is in motion.Here's what I want to do,I want to replace the headlights with bright white LEDs and add 2 extra Red LEDs in the rear. I'll solder the LEDs on the PCB using wires in series.While I was researching on the same, I found out that the LEDs might require me to upgrade my power source. As per Wikipedia (, white LEDs need a voltage of 3.5 volts. So probably, when the car is in motion, the following will be in constant useForward: Motor 1 + 2 Front LEDs (3V + 7V i.e. 3.5V x 2) Nominal LoadReverse: Motor 1 + Rear LEDs (3V + 4V i.e. 2V x 2) Nominal LoadTurning while moving Forward or reverse: Motor 1 + 2 Front or Rear LEDs + Motor 2 (3V + 7V/4V + 3V) Full LoadSo, here's another thing, I don't want the LEDs to dim when the car is in motion or the car to slow down when it is turning. Neither I want the the car to go faster when it is moving i one direction (i.e due to less load on batteries). I mean I don't want the motors to be get extra voltage when the car is in under nominal load condition neither I want it to slow down or the lights to dim, when it's under full load condition.Do I need to upgrade my power source i.e from 4.8V?If yes, then can I use 2 9v Rechargeable 175 mAh batteries?Also, as per the link below, to connect the LEDs in series, I would need to add a resistor to the LEDs, which will take another 2V]Connecting LEDs in SeriesIs that correct?Also, lemme know if I would need to upload pics of my PCB.

Topic by saurabhvarma 9 years ago  |  last reply 9 years ago

How To Turbo-Charge My LED Light String

I am new to electronics, but I have an idea and hope that it’s simple enough for some of you with more experience can tell me I’m either on the right track, or complete wasting my time. I have looked at a number of basic solar light / charger circuits in here and on the Web, and have a very basic grasp of how they work, but the intricacies and exceptions are still fuzzy to me.  I don’t want to recreate the circuits, and want minimal soldering since I’m new to that too. I have a 40 foot long string of 100 LED solar lights that are driven off of one hard-wired AA Ni-MH 1200mah battery.  There are three ideas I have to supercharge the string to improve it.  Without tracing through the existing circuit (which I may not understand anyway), I want to draw on your experience before I get too involved. If I ultimately need to pull things apart and try and trace the circuit, I will, but until then, your guidance would be appreciated. I would like to: A) Remove the old battery and add a larger capacity battery since I currently get maybe three hours of light.  Probably easily done. 1. Changing the battery to a larger capacity looks straightforward.  I will be adding a D cell (if it fits the case) NI-CD with 3000-5000mah (not purchased yet).  Since the cell is the same voltage, can I assume that the swap doesn’t really affect the circuit? B) Add another solar panel.  Probably easily done.  1. I have one small solar panel that came with the unit which feeds the existing battery.  I am assuming that it is 2v (to suit the AA battery) and based on the size, I am assuming that it is between 100 and 150ma peak output.  I would like to add another small panel that I have lying around that is rated 2V / 150ma.  Installing these in parallel should give me a higher energy input, but still at the 2v. Looking at the circuit board the solar panel goes to the board before the battery.  I am assuming that the only thing between the solar panels and the battery is the diode, and that there isn’t any sort of current / voltage limiter on the board.  Can I assume this? Is the diode likely to handle me doubling the power through it? 2. My calculated peak solar power for the two looks to be about 250 to 300ma.  By following the 10% rule for charging and assuming that I’ll likely not get 100% rated solar power for long,  I’m assuming that I my D-cell should handle the trickle charge? C) Increase the power through the white LED’s.  This is my main question, and biggest uncertainty. 1. I am assuming that driving 100 lights off of one battery does not really get close to the maximum.  I pulled the shrink tube off of one of the LED’s and it appears a simple parallel connection.   I don’t see any resistors that are inline with the LED bulbs or directly before or after the LED string wires on the board. I’m assuming that I can add a resistor in series with the light string. Will the light output change much? How can I figure out what resistance to add without blowing my LED’s? Am I on the right track? With my very rudimentary (and possibly wrong) multimeter skills, I tried to find the following as well: Battery voltage – 1.16 v Voltage (measured as parallel with the light string) – 2.56 v Current (measured in series with the light string) – 13.1ma (this sounds low?) I’m slowly learning my way through this, and I want to put together an ‘ible together when I’m done.  Any help, corrections to my assumptions or suggestions you have are appreciated. Sorry for the long-winded message. Craig

Topic by harley1974 7 years ago  |  last reply 7 years ago

Need help sourcing a battery for my project?

I'm in the development stage for my next couple of projects, and after thinking about variables and other such random stuff, I've decided on a project (no, I won't tell you what it is. not yet at least!). The project is going to have to be very small, and will really be stretching the limits of through hole soldering (I dont want to to SMD on this). Due to size constraints, and power consumption, I need a very specific size battery. I need a battery with (I hope) at least 700mah capacity, if not more, as well as be rechargeable. Diameter should not exceed that of an AAA battery (around 12mm or so). Voltage CANNOT be 1.5, and must be more than 2v (single batteries only please! Multiple cell batteries are fine, as long as they are in a single package). Length of the battery can be pretty long, but should not exceed more than 40mm or so. Battery can be any rechargeable type, with the exception of Li-ion flat packs (I think they are a bit too fragile and volatile for a project exposed to daily wear and tear.). My current choice is a 123A li-ion 880mah battery, but it is a bit too wide for me.. Anyone know of a good, rechargeable, small battery? I know this is really stretching my choice limits, but I would GREATLY appreciate any help you give. Many, many thanks in advance,  -Thomas

Question by astroboy907 6 years ago  |  last reply 6 years ago

Step up 6 volts to 9 volts? Halp!

I have a GB Instruments dmm i got at a Hamfest (Ham Radio Fest) in Peoria, IL a few years back for like $6. It's great, and its more accurate than my father's Craftsman from Sears that he paid $40 for about a year ago. I have replaced the 9 volt battery twice in it. 9 volt batteries are horrible for capacity, and I use this DMM so much it's almost a high drain on the 9v. I know that a standard 9v holds 500-700mAh. I have a whole box of old AAA batteries that have about 1.4+ volts still in them from a stupid car toy that drained an AAA .1v-.2v and called it dead. A standard AAA alkaline battery (E92 or equivalent) holds 1,200 mAh or 1.2Ah@1.5v. 4 alkaline AAA batteries holds 4,800 mAh@6v. I can fit 4 AAA batteries in the 9 volt holder in my DMM snugly with a piece of foam for anti-rattle. That's only 6 volts. The DMM will power on very dimly at 6v, so is there any circuit to make up for the lost 3 volts without adding a bulky power pack? There is a LOT of room in the DMM for mods n stuff. Thanks for any help Is there any way to step up

Question by lilpepsikraker 9 years ago  |  last reply 9 years ago