Author Topic: completely confused about power supply  (Read 1031 times)

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Offline 123laurensTopic starter

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completely confused about power supply
« on: August 30, 2011, 12:19:09 AM »
so, my robot currently works well, codes fine and stuff... but the only major problem I have is power limitations. currently an ardurino uno is being powered by a 9V battery, and the 3 servos by 4X AA beteries, and the they both run out in 5 minutes.
another problem, I can only buy from here: http://www.netram.co.za/vmchk/Electronics/Power/View-all-products.html because I live in South Africa.

obviously I will be forced into using Lithium Ions, because that is the only type they sell. but they say 1 sell is only 3.5V or something, and then I need to power 3 servos and a ardurino, and charge them. how whud I wire this? and charge using what? and how do I connect the servos and UNO?

Offline 123laurensTopic starter

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Re: completely confused about power supply
« Reply #1 on: August 30, 2011, 01:58:41 AM »
http://www.netram.co.za/Power/Lipo-Rider.html
this looks promising... it outputs 5V via USB for my UNO... but will it convert the battery's 3.7V? if it is 3.7, it seas that's for 1 cell, and it doesn't say how many cells...
and is it powerful enough to power servos for longer than 5 minutes???

(battery im talking about: http://www.netram.co.za/Power/Lithium-Ion-Battery-1600mAh/ilvm_fly2_grey.tpl.html )

Offline Soeren

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Re: completely confused about power supply
« Reply #2 on: August 30, 2011, 12:41:46 PM »
Hi,

Please use "Modify" to keep to a single post, that makes it more likely to get everything answered.

so, my robot currently works well, codes fine and stuff... but the only major problem I have is power limitations. currently an ardurino uno is being powered by a 9V battery, and the 3 servos by 4X AA beteries, and the they both run out in 5 minutes.
What kind of AA's, Primary cells, NiMH, NiCd or what?

A fresh set of 4 AA's should be able to run two servos for at least 45..60 minutes.
Did you use buffer capacitors on the motor leads?

It could be the internal resistance/impedance of the battery that make it appear flat. Did you measure the battery after it stops running the 'bot?


The boost circuit you linked to won't cut it, as it says "Up to 5v 350mA supply ability" which is far from enough for even a single servo.
A 1Ah LiPo cell will have around 3.3Wh (depending on discharge magnitude), while a set of 4 AA Alkalines will be around 12..15Wh (varies a lot between manufacturers
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline 123laurensTopic starter

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Re: completely confused about power supply
« Reply #3 on: August 31, 2011, 02:02:15 AM »
Hi,

Please use "Modify" to keep to a single post, that makes it more likely to get everything answered.

so, my robot currently works well, codes fine and stuff... but the only major problem I have is power limitations. currently an ardurino uno is being powered by a 9V battery, and the 3 servos by 4X AA beteries, and the they both run out in 5 minutes.
What kind of AA's, Primary cells, NiMH, NiCd or what?

A fresh set of 4 AA's should be able to run two servos for at least 45..60 minutes.
Did you use buffer capacitors on the motor leads?

AA type... I'l see that... they are very cheap though. I honestly don't know much about batteries.

no, I did not use capacitors. do you just attach a large one on the + line or a ceramic between the + and -? I do still have a large capacitor lying around...

mmm...what about 2 of those batteries linked in series, make enough power to make both work?

when the 9V runs out, the chip seems to keep resetting... is that what is meant to happen? also this  collects data from an IR rangefinder, can the noise be a cause of the resetting? apparently these are very noisy.

Offline Soeren

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Re: completely confused about power supply
« Reply #4 on: August 31, 2011, 12:20:57 PM »
Hi,

AA type... I'l see that... they are very cheap though. I honestly don't know much about batteries.
Might be carbon/zinc then and if, they're no good.


no, I did not use capacitors. do you just attach a large one on the + line or a ceramic between the + and -? I do still have a large capacitor lying around...
A large cap from positive to negative on the motor supply.


mmm...what about 2 of those batteries linked in series, make enough power to make both work?
If anything, you should connect them in parallel for a higher current, but you'd be better off with some NiMH cells and they're much cheaper in the long run.


when the 9V runs out, the chip seems to keep resetting... is that what is meant to happen?
Yes, it's not that different  from being choked - except you better hope someone can "reset" you  ;D
If the 9V battery gets discharged under what's needed for the voltage regulator to keep a stable voltage, the controller may go into reset and as soon as the load on the battery lightens, the apparent voltage will rise, the load is reapplied and soon you see this repeating.

The worst kind of cells are the carbon/zinc type, as they have the highest internal resistance.
Somewhat better is Alkaline batteries and if you have too much money, you can get really tough lithium primary cells (I use them as backup for my DSLR).
Rechargeable cells i a must when you want to run motors regularly and NiMH is the best choice all round, if you don't wanna spend the extra on Lithiums. NiCd has got a much lower internal resistance, but unfortunately, they only come in capacities around 1/3 of NiMH.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline 123laurensTopic starter

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Re: completely confused about power supply
« Reply #5 on: September 01, 2011, 02:37:20 AM »
Hi,

AA type... I'l see that... they are very cheap though. I honestly don't know much about batteries.
Might be carbon/zinc then and if, they're no good.


no, I did not use capacitors. do you just attach a large one on the + line or a ceramic between the + and -? I do still have a large capacitor lying around...
A large cap from positive to negative on the motor supply.


mmm...what about 2 of those batteries linked in series, make enough power to make both work?
If anything, you should connect them in parallel for a higher current, but you'd be better off with some NiMH cells and they're much cheaper in the long run.


when the 9V runs out, the chip seems to keep resetting... is that what is meant to happen?
Yes, it's not that different  from being choked - except you better hope someone can "reset" you  ;D
If the 9V battery gets discharged under what's needed for the voltage regulator to keep a stable voltage, the controller may go into reset and as soon as the load on the battery lightens, the apparent voltage will rise, the load is reapplied and soon you see this repeating.

The worst kind of cells are the carbon/zinc type, as they have the highest internal resistance.
Somewhat better is Alkaline batteries and if you have too much money, you can get really tough lithium primary cells (I use them as backup for my DSLR).
Rechargeable cells i a must when you want to run motors regularly and NiMH is the best choice all round, if you don't wanna spend the extra on Lithiums. NiCd has got a much lower internal resistance, but unfortunately, they only come in capacities around 1/3 of NiMH.

well, I don't think they sell NiMH batteries...
so... you suggest I buy rechargeable AA batteries and 9V (dont remember the letter, D?) batteries of some strange type, or do you suggest I buy cells from netram...
and hook up a large capacitor between positive or negative(those small yellow-greish ones or the large plack or blueish ones? sorry for my electronic noob-nes)  from my knowledge I think it is a yellow-ish one, evens out the power,right? darn electronic kits don't teach me those names...
I guess buying good-quality rechargable AAs is simpler and less expensive than those cell thingys with their fancy plugs and oddly working chargers.

Offline Soeren

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Re: completely confused about power supply
« Reply #6 on: September 01, 2011, 07:59:31 AM »
Hi,

Please only quote the text needed to get answers into context, or leave it out completely :)

well, I don't think they sell NiMH batteries...

Not according to their web site.


so... you suggest I buy rechargeable AA batteries and 9V (dont remember the letter, D?) batteries of some strange type, or do you suggest I buy cells from netram...

9V batteries are usually just called 9V's or "9V transistor battery" (or PP3 which is their form factor).
Some 9V's contains 6 AAAA cells (Not the Duracell variety however).
D-cells are the beefy 1.5V cells used in large flash lights
C-cells are in between AA and D

For now, I think you'll find it much easier with NiMH cells.
Here is what I think is a good deal - 4 AA's (2450mAh), 2 AAA's and a charger for both types at R135 (around $19) and then you've got a charger too, probably not a super fast charger, but I think it will be a very good starting point.

To that you'd have to add a shipping fee, but as they write (on their home page)
Quote from: Bios Online
Bios Online ships anywhere in South Africa for a nominal fee.
# We offer FREE DOA (Dead on Arrival) Insurance. This means that if your product has a manufacturer fault when it arrives, we will replace it at no cost to you!
# Orders ship to major centers within 1 working day, while outlying areas can sometimes take 2-3 working days. Our deliveries are only made during normal working hours.



Another option is [urhttp://www.dinodirect.com/rechargeable-batteries/currency-ZAR.htmll]DinoDirect[/url], who's got worldwide free shipping.
You could get a very cheap setup running 2 of these sets in parallel and they're only marginally higher priced than lousy carbon/zinc cells.

DealExtreme does have cheap batteries too
It should however be mentioned, that it's common for all the Chinese websites to overrate their batteries a fair bit.


and hook up a large capacitor between positive or negative(those small yellow-greish ones or the large plack or blueish ones? sorry for my electronic noob-nes)  from my knowledge I think it is a yellow-ish one, evens out the power,right?

Hehe, don't worry, back when I was in the engineering academy, a fellow student asked the teacher how many blue ones went for a yellow one (perhaps not a wonder that he didn't pass and is now a bus driver).
I don't know how well it went down in your country, but in electronics, it's much like in Michael Jacksons song Black or White ;D
You should never judge on color (neither humans nor components), as it's the inside that counts!
Here's your homework for tomorrow - there will be an exam :P  ;D

Close to halfway down, you can see pictures and description of different types of caps.
For buffering a battery/servo combo you'd need (wet) electrolytics and the larger the better, but getting NiMH cells will help and you'd only need it a smaller electrolytic cap for smoothing out a bit.


darn electronic kits don't teach me those names...

If you want to learn stuff, just hit Google with "[subject] tutorial"
Eg. "servo tutorial" will yield this
(With the two top hits leading to this very site).


I guess buying good-quality rechargable AAs is simpler and less expensive than those cell thingys with their fancy plugs and oddly working chargers.

Yes, for now I think the Bios Online set is your best option.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline 123laurensTopic starter

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Re: completely confused about power supply
« Reply #7 on: September 01, 2011, 10:25:43 AM »
well, lucky for me I have a (SERIOUSLY old) charger lying around, witch can charge 1 9V and 8 AA batteries at the same time. if it still works, that is. and for worldwide free shipping, we have to pay "import tax" and its this whole system of the government E-mailing you threatening to cancel the package and so-forth. i can probably buy these batteries in a supermarket as well, just need to write down that NiMH thing. and i did not read that capacitor tutorial, way too long and boring looking, and a bit crazy.

basically here, most of my knowledge came from "300 in one!" sets. its basically lots of components lots of wires, and the wires fit in these spring things. these sets then came with all sorts of stuff. 555timers, capacitors of 20 values, same with resistors, even a 7 segment display. and then you get this huge manual. the other 50% came from Wikipedia, due to my interest in these sets.

shortly after my electronic Googleing I got interested in programming(actually way more interested, I already coded at the time and made the game "ho am I?" at the age of 6, yousing a program called Game Maker. and yes, I did spell it like that for some reason. fun game, though)and this I couldn't, or didn't want to, learn any further.

Offline Soeren

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Re: completely confused about power supply
« Reply #8 on: September 01, 2011, 12:12:52 PM »
[...] i did not read that capacitor tutorial, way too long and boring looking, and a bit crazy.
Well, if you find reading and learning too boring, then you won't get very far in robotics.

I find people not wanting to do what it takes for their own learning experience much too boring to bother with.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline 123laurensTopic starter

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Re: completely confused about power supply
« Reply #9 on: September 01, 2011, 11:51:10 PM »
[...] i did not read that capacitor tutorial, way too long and boring looking, and a bit crazy.
Well, if you find reading and learning too boring, then you won't get very far in robotics.

I find people not wanting to do what it takes for their own learning experience much too boring to bother with.

but I already know how capacitors are used! just not all 100 types. only the ceramic and electryic (see? I did read some of it) (I did spell it right, right?) ceramic are non-polatary, so they can be charged in any way, but don't just let power trough. then the electryic things have a much larger capacity, but must be powered the right way(or it will explode, apparently,seas the crazy tutorial) and are used in timed things to a camera flash. I hope all that was correct.

anyhow, currently my problem is not capacitors(although I still don't know how I am meant to remove noise...not important) but it is batteries. I will try to find the NiMH batteries tommorow, or the day after. I found this store that sells everything battery related. solar panels, car batteries, chargers, something between a car battery and a 9V (a mini car battery with a 9V plug on the top,how odd) so I might find it in there. thanks for all the help so far!

Offline Soeren

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Re: completely confused about power supply
« Reply #10 on: September 02, 2011, 02:41:56 AM »
Hi,

but I already know how capacitors are used!
Mmmm sure and you only ask because...?


just not all 100 types. only the ceramic and electryic (see? I did read some of it) (I did spell it right, right?) ceramic are non-polatary,
No, they are non-polarized


so they can be charged in any way, but don't just let power trough.
They don't let DC through.
AC is another fish altogether. In single supply audio amps there's a large capacitor in the output and the power zips right through it.
Don't touch the mains through a capacitor, or you'll get instant proof that caps let AC through.


then the electryic things have a much larger capacity, but must be powered the right way(or it will explode, apparently,seas the crazy tutorial)
I'm sure Tony lies sleepless over you calling his, very well written, tutorial crazy, but as a matter of fact, yes, they blow if polarized wrong (as most people with some experience probably have tried for fun at least once). Even an LED can go with a large *crack* if you try to feed it too well - I separated a 1W LED from it's package (glued to a heat sink) very suddenly (by accident) a couple of weeks ago - apparently it didn't like 10A :-\


and are used in timed things to a camera flash.
I seriously don't understand that sentence?
Electrolytics are the worst caps to use in timer circuits, as their capacity is very temperature dependent.
You use an electrolytic in a flash to store some 300...500V for the discharge.
I cannot imagine how these two statements can be rolled into your sentence?


anyhow, currently my problem is not capacitors(although I still don't know how I am meant to remove noise...not important)
Not important?  Even if the noise interferes with your other electronics, rendering it inoperable?


but it is batteries. I will try to find the NiMH batteries tommorow, or the day after. I found this store that sells everything battery related. solar panels, car batteries, chargers, something between a car battery and a 9V (a mini car battery with a 9V plug on the top,how odd) so I might find it in there. thanks for all the help so far!
Just stick to the NiMH's for now. Solar panels and odd looking batteries are a step or two up the noise reduction part  ;)
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline 123laurensTopic starter

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Re: completely confused about power supply
« Reply #11 on: September 02, 2011, 11:14:50 PM »
 well, since i don't know enything about capacitors, can you please tell me how to wire the noise reduction on both power supplies? sorry that i  had to teach myelf, ad that these kits i learnt from dont tell me how it works, i do understand the 555 timer IC and some useful circuts you  can make with them(i dont memorise all 300, though).
at least i have already made a robot, and not still posting "will this work?" sorry noobs out there,i will admit i was one one of them. but i didn't say "my idea doesn't work, i quit".

Offline Soeren

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Re: completely confused about power supply
« Reply #12 on: September 03, 2011, 06:46:36 AM »
Hi,

well, since i don't know enything about capacitors, can you please tell me how to wire the noise reduction on both power supplies?
It's not the power supplies that need noise reduction (a battery doesn't generate noise), but motors and actuators do and sensor circuits may need noise filtering in some cases

Since you're using servos, you cannot mount noise caps directly on the motor (without opening the servos), but you can loop the wires going to them through a ferrite toroid (ring core) one or two times, as close to the servo as reasonable doable, to dampen a lot of the noise it generates and if you have your power feeds fed fairly directly to the power source, you shouldn't need to do any further.

You could mount buffer capacitors on the supplies, which is just mounted in parallel, but wait and see how well rechargeables work, before doing this.


at least i have already made a robot, and not still posting "will this work?" sorry noobs out there,i will admit i was one one of them. but i didn't say "my idea doesn't work, i quit".
Good, now you just need to read that cap tutorial and find one on batteries  ;D
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline 123laurensTopic starter

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Re: completely confused about power supply
« Reply #13 on: September 04, 2011, 12:18:46 AM »
out of boredom, just did.
i knew 40% of it already, or read it before. it waas quite good though.
still dont see how that helps me.
and it DID say electryic capasiors were ued in timing circuts. HA! i even half remembered how they work, those circuts. the time it takes to discharge, i believe.
and i need to put a coil around the servo???hu?

Offline Soeren

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Re: completely confused about power supply
« Reply #14 on: September 04, 2011, 07:58:56 AM »
Hi,

still dont see how that helps me.
Yeah, you probably think the same about school   :P ;D


and it DID say electryic capasiors were ued in timing circuts. HA!
It's a bit old and Tony doesn't use microcontrollers. Going back in time, they were the only option (and E-cells never really caught on that well) for long delays in small circuits, but doing it these days would be stupid, as you can get delays ranging to years with 1% precision for less than 50 cents.


i even half remembered how they work, those circuts. the time it takes to discharge, i believe.
Time spend refreshing it is not lost and the purpose was to know the difference between cap types.


and i need to put a coil around the servo???hu?
No. Re-read what I wrote.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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