First steps in using the Sun's energy

[birrbert]

You still didn't say the exact name of the LDO. Knowing that, would help me a lot in understanding.

Also, try connecting some other type of load instead of the phone, like a small fan that consumes less Amps than the phone, or a small 4-5 Volt light bulb or anything that accepts 5 Volts and consumes little power. Cell phones and especially smart phones usually need 500 mA more or less stable current, otherwise they won't even start charging.

I personally tried the LM340T-5 voltage regulator. Technically this is not an LDO, because it needs at least 7.5 Volts input for 5 Volts output, but it worked. I powered it from an adapter, it gave stable 5 Volts and enough Amps to charge the cell phone.

PS: nice assistant you got there.

[dr_p]

Under the link below is my film with my attempt to charge my phone using 4 AA batteries and LDO regulator - failed. If you have any idea what am I doing wrong I will appreciate your suggestions. Sorry, I've tried for over one hour to post a youtube film directly in here instead of a link but failure again. None of "posting youtube video into a forum" worked for me. 

http://www.youtube.com/watch?v=Au4tL3gGnz4

The phone's eating the 7mA, so it's battery seems to be almost full.  Put some other load or discharge the battery and try again.

[gording]

Hi

Sorry, silly me. At the beginning I thought that just saying it's a 5V LDO explains everything Now I know it doesn't. Ok so it is LM 2940
http://electropark.pl/attachment.php?id_attachment=471
By the way, does anyone know if those capacitors witch manufacturer suggest to install on that LDO are really necessary and what for? (Keeping in mind what do I use it for) I did installed them however they are a pain in the a...  Very tiny, difficult to solder on an LDO and already fallen of couple of times. I just can't solder them on properly. I have couple of this LDO's. When I connected one without capacitors I didn't realized any difference in the voltage nor in the amps.
The phone's battery I was trying to charge was almost discharged - showed only 10% charge so it is not the issue dr_p suggests.

I allso connected for a short period of time batteries directly to phone, without LDO. Voltage was around 5,5V and again only 20mA flowing. I did also connected other phone (with LDO again this time - didn't want to damage it) Same problem 7mA.
I'm waiting for some free time during the day to try to do the experiment again but instead of 4 AA batteries use my solar panel.
Other idea I've got is to repeat experiment but using this time 4 AA rechargeable batteries. 4*1,2V (1,3V) should give nice 5v, and no need for an LDO, and then see how many mA flows into the victim phone.
Maybe it was the batteries I used. Maybe they were the problem.
 Anyway when the charge controller arrives - the one which birrbert also ordered and 5v step up converter the LDO will become unnecessary.

 

[SeanB]

The capacitors are needed, otherwise you will find there are input voltage and current combinations along with certain loads which make it a very good oscillator. This is because the control loops are invariably a lot faster in reaction than the very slow PNP lateral transistors used in the LDO to give a low dropout voltage. The capacitors slow the loop response time down so the control loop has low enough gain so as not to oscillate. You will find you typically need 100uF or more to make them unconditionally stable at all loads.

[gording]

Thank you SeanB - now I understand

I've made a little progress and see what have I discovered:

http://www.youtube.com/watch?v=FSzpMTeBYu4


Also under here's the video with my other concern: Is it normal for an 5V LDO LM2940 to give 5v on the otput without load but only 4,3v under load conditions?

http://www.youtube.com/watch?v=kvomU_Y15Y4

If you'd like to see my solar panel that's how it looks like:

http://www.youtube.com/watch?v=HYmqLhKaJKA

[birrbert]

Hey Konrad!

I have a same cheap, yellow multimeter like you and now that you started working with it, I noticed something: I think that for measuring milliAmp you have to put the red probe in the other red socket. So, Volts and Ohms and milliAmps use the same red socket and only the Amps are in the second red socket. Please check with a load that pulls 200 mA max and I'm pretty sure this will be the situation. I don't have the possibility to try it right not.

Regarding that alligator clip cable that you use, I have no idea what's going on. I also have those and they seem to be very low quality. I "disassembled" like three or four and put the alligator clips on new, thicker cable. Maybe I should do this to all of them to avoid future confusion, otherwise these damn small details make me go crazy. Yeah, beginner's mistake that the last place to search for the problem is the cable.

Regarding the LDO, I tried a similar one that you have, MCP1825S-5002EA. According to the datasheet it accepts 6 V input and can give 5 V output / 500 mA. Under no load conditions it does what is says, but under load it can output less, just like yours. This could be due to losses or resistance in the cables/connections/breadboard/etc. or we are missing some additional components or simply this is general behavior. In my case I don't remember the exact numbers, but I know that without load it was 5 V and with load it was 4.(something)...

[Mr Eastwood]

I've made a little progress and see what have I discovered:

Hi,   I think it might be your multimeter;  I was looking for an circuit diagram of your meter and stumbled on this page which describes a meter similar to yours and they appear to not have a very good input impedence.  http://tubesound.com/2011/05/13/limitations-of-cheap-meters/  Could this be the reason for the weird readings?

[birrbert]

Hi! I couldn't stand not to test a few things. Results below.

Multimeter and measuring mA
I wrote that I have the same multimeter as Konrad so this meant that I could do Amp measuring. I had a fan that consumes only 40 mA at 5 V. I connected it in series with the multimeter and started measuring current. The circuit was working only when I had the red probe in the 10 A (top red) socket, although it's clearly written on the multimeter that the Volts/Ohms/mA are measured using the red socket situated between the 10 A socket and the black one. Please see attached photo!
Anyway, I flicked the dial through all the mA ranges and there was no change like in Konrad's case, i.e. I saw 40 mA everywhere. Still, it's weird to see one thing shown on the multimeter and get a different result. The question is, why is this and why would they put the mA measurement together with the Volts and Ohms in the first place?

LDO, 6V/5V
I took my MCP1825S-5002EA in TO-220 package and took measurements. Input was 6 V and I used no additional components, just the LDO, cables and the fan mentioned in the previous paragraph.

- no load: 4.94 V.
- load: 4.93 V on the LDO side and 4.71 V on the fan side.

Again, this difference on the two sides of the cable occurs, just this time it's much smaller than in my post about the step-up converter (4 V vs. 2 V).

[tipidsolar]

Hi Masters,

Sorry im just a newbie here even into these Solar power things. Im form Philippines , as you have heard we where hit by the Strongest Typhoon Landed on the planet. Up to now our Brgy.. in Ormoc City Leyte still doesn't have electricity So im planning to build a simple solar power system setup . My target is

1pc -100 Watt Solar panel 12v
1pc - 20 amp Charge Controller prepare to use the PWM budget wise because MPPT is expensive here.
1pc - 100AH Deep Cycle Battery
hope this setup can run 5 LED 4 watts and 2 Stand Fan 12v @ 15 Watts ( which im planning to use whole day? )
would this be possible ? as i am not familiar with the computation.

Please guide me doing my first Solar Setup

Thansk,

[SeanB]

You might want to get a second panel to charge the battery and also have enough power to do things like charge a cellphone or two during the day or run a laptop. Currently the 100W panel will barely be able to charge the battery with the constant fan load, and will take over a week to fully charge the battery. Fine for an intermittent load but you want more than the single panel can do. Thus a second panel in parallel with the one and going through the same charger will work. The battery is capable of running the lights all night along with the fan provided you put the energy back the next day along with the losses.

[tipidsolar]

@SeanB

So does it means that 100watts panel cannot fully charge the 100 AH battery ? does the 2 stand fan which is 12v DC 15 watts cannot be accommodated by the 100 watts panel? like how many hours it can run?

How may hours can a deep cycle 100 AH battery if being uses in 30 watts?

Sorry for being noob sir .

What if i only use the lights for 4 hours and let 2 lights run over night and 2 stand fan running over night?

Thanks in advance...

[SeanB]

100W panel typically will charge the cell at around 4-5A, and usable time will be around 8 hours in a typical sunny day, giving you a charge return into the battery of  between 30-50 Ah back into the cell. You will need 2 days to fully charge the battery from flat with no draw, and typically it should have enough capacity to not go below 50% charge if there is no sun for a day or two. Fan draw is around 1.5A, and over 24 hours it will use about 40Ah of the battery capacity, and will basically take around a third of the charge current through the day. Lights will use about 20Ah if they are on from sunset to around sunrise ( assuming 2 are running all the time and 2 are off at around midnight) so your battery will slowly discharge each day until it goes flat. Just not enough energy coming in.

What you want to get is a good first start, but you will find that you need to use less power so that you do not damage the battery.  You will need to cut the load somewhat, so using a fan for a few hours and not all night, and having only one light on all night with the others being off around 10PM will keep the load low enough that the battery does not go flat, which will damage it capacity wise if done for only a few cycles. a second panel will enable the panel to charge the battery fully each day, and will give spare power to run eg the fans during the day as well.

[tipidsolar]

Thanks for the Quick reply SeanB.. How about on day time can i still use my Fan running while charging?

a second panel will enable the panel to charge the battery fully each day, and will give spare power to run eg the fans during the day as well.

How about buying a MPPT charger than additional 100 watt panel? ived watts one of the video saying that because im using regular charge controller their are chances i will lost 40% from 100 watts?

Therefore your recommendation would be like this?

100 watt panel
1 charge controller
1 fan 12dc v 15 watts ( how many hours is the maximum?)
4 Led lights which only 2 off by 10 pm while 2 running over night?

or can you give me more detail specs for my setup.. 


Thanks

[gording]

Hello:)
It's been couple of months since I wrote last in this topic. However my project has evolved and if you'd like to see how it looks right now please watch the wideo under the link below.
http://youtu.be/7kSss09-kjQ

[birrbert]

Welcome back gording!

It's nice to see that you got something working, but I think you don't need two step-up converters. You should let the Li-Ion charger to charge the battery directly; I wouldn't put any step-up converter there. I would put the step-up converter only at the end of the circuit to step-up the the 3.7 Volts coming from the battery to 5 Volts. I would experiment with different types of step-up converters to figure out which one does a better job. I will actually do something like this since now I have a working power supply which I can use when there's no sunshine.

Also, I've been thinking a bit. I'm not sure, but experimenting with this type of solar charging might be useless in some regards. It might be OK for somebody if the goal is to learn, but otherwise it's useless, because others have done it before and have done it in a professional way, for example Adafruit or Brown Dog Gadgets. I'm just a bit unsure what kind of new stuff can we add to the topic?

Doctor, I'm so uncertain lately! Or maybe not?