Anybody done batteries management before?
I'm working on a wireless handheld controller, still looking for suitable battery solution and charger. Would prefer to build my own charger but it's too risky for this project, maybe next one.

Anybody know where can I get suitable battery & charger at reasonable prices? I need at least 7.2v 2000mAh. Those RC hobby shop mostly don't provide any datasheet, don't know how long they'll last.

Huhu, im making research on fighter robot right now. weight less than 1kilo.

Fully autonomous, and using pic. Any idea on what material should i use for the body? before this im using arcylic, but that for sumo and maze competition. Now robo fight, should be stronger body right?

On behalf of the Robotics Club of Multimedia University, we wish to invite you to participate in an upcoming event which is The Robotics Challenge Week (RCW) where it will be held in the Main Hall building at Multimedia University Campus Melaka.

The primary goal of this event is to
-inspire people, especially to the public,
-to learn more about Robot Science through robot demonstration

This event is hold on 10th-12th july 2009 and it is a national level event
which we invited Universities around in malaysia for Robot competitions and
some secondary schools from Melaka to introduce them what is robotics all
about.

Some of the robotics related company will be invited as an exhibitor too.
Our main idea for this time is to publicize the Robotics and Automation,
same to the education side.


we are looking for
sponsor/advertiser/exhibitor/vendor too

SPONSOR
any kind of sponsor are welcomed(goods,voucher,etc..)
we'll provide you a proposal.
we can discuss about the benefits.

ADVERTISER
you can promote in our booklet, banner, bunting all kind of promoting materials. contact me for the rates.

EXHIBITOR
for exhibitor your main objective is to exhibit your product, in this case we will not charge you a cent but you are not allow dealing during the event.(preferred electronic based)

VENDOR
for vendor we will charge you an amount and you are allow to do business there. contact me for the rates.

ROBOT COMPETITION REGISTRATION CLICK HERE

Official Website: http://rcw.mmurobotics.com

CONTACT

Best regards,

Choong bing hung
012-7316713
016-7736713
dabing63@hotmail.com

Assistant Director of Sponsorship&marketing
Robotics Challenge Week 2009
Robotics Club
Multimedia University Melaka, MMU

This post has been edited by binghung: Apr 27 2009, 11:36 PM

Have you found the answer you are looking for? There are a few types of battery available in the market, the most popular one are namely the Lipo and NiMH. Lipo are more expensive than NiMH, however they are lighter and provide better current output. Retail charger for Lipo are also much more expensive than NiMH. If you are looking for cheaper battery, I suggest you try the typical rechargeable battery (GP, Sanyo, Energizer). You would need 6 cells, 1 NiMH charger, which come to about RM100++.

There aren't any datasheet for battery (I have yet to come across any ) Unless you application is drawing high current, it should do fine. Estimation for rechargable battery duration = (mAh rating) / (mA drawed by circuit).

With 2000mAh battery, it would last you 1 hour for 2000mA circuit, or 2 hours for 1000mA circuit, and etc.

Actually, I am (just started) planning to build my own Lipo charger. Still doing some reading here and there.

Anyway, I am also looking for a suitable high current (10-15A) voltage regulator, from 7.2VDC to 6.0VDC. I have yet to find the right chip, or circuit. Any recommendation? Anyone?

This post has been edited by Aurora: May 8 2009, 11:23 PM

Hehe didn't expect any answer from here..

Anyway I've settled on either Li-ion or NiMH battery, Lithium based preferred after reading Battery University. Lot's of good information about batteries there including battery charging graphs.
I'm getting both the battery and charger from Farnell. I can't really trust those from hobbyist shop, only info I found is they are made for high current discharge, 10C, 20C and upwards, while their lifecycle is only like 30 to 50.
My current requirement is much lower, ~300mA peak, average is probably less than 50mA. Battery needs to last at least 8 hours before recharging and I need to make sure the battery can last for at least 1 year of usage.

I'm not building the charging circuit this time, but from what I gather, accurate voltage sensing, and current control is very important to have maximum battery lifetime. I'm not sure why you need the 10A requirement, but a linear voltage regulator with 10A output will be very large (needs lot of heat sink) and inefficient. Building a switching regulator on the other hand is like a project on it's own already (another project I've always wanted to do )

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Added on May 9, 2009, 12:27 pmOh yeah, you'll need temperature monitoring, and maybe separate cell balancing for a really complete charger

This post has been edited by tgrrr: May 9 2009, 12:27 PM

Where did you get the information that the RC rechargeable liftcycle is 30 to 50? Those are Li-ion/NiMH, shouldn't all their lifecycle standard? Which is 500-1000? Care to share the link?

I'm trying some linear regulator now, the low dropout type. With that, I'm still throwing some 12W of heat. Not that practical. I need those 10A to drive few motors I found this link High Current Regulator Supply using LM317.

I'm new to electric power, not aware of switching regulator, I'll start looking and see what I can get

Um.. I don't have the link, but I was searching through foreign website that sells R/C stuffs (looking for datasheet or more information), and I recall they mention the current output capability together with the number of cycles (maybe guaranteed to work?).
Well my opinion is, at 10C to 20C, they are draining a 2000mAh battery at 20A to 40A. That kind of usage might perhaps be the reason of the low number of cycles, which means perhaps moderate usage won't have any issue.

The High Current Regulator Supply is only 2 A. Anyway for ~3A, there are some single regulator choices, LM307 or something like that, in TP03 or T03 package (looks like a big metal transistor with 2 legs, the body is ground). The key with linear regulator is heat dissipation, so with adequate heat sinking, maybe can go up to 5A. And another big consideration is the transformer, it'll be huge to be able to supply 10A. Make sure the secondary winding can sustain 10A of current!

Switching is dangerous, as it plays with high DC voltage, and requires active control by uC. That means feedback isolation is required.

Probably right. RC motor draws high Amp. But battery technology is pacing. The battery university link was written few years back. (No wonder I can't find any info on Lipo). Lipo technology has advanced since it was first introduced few years ago.

I have the LM317 (max 1A), and LM338 (max 5A) continuous application. The LM338 is in TO3 form as you described. I have not try it, my circuit is still not ready

I plan to use Lipo 7.2 VDC (at least 4000mAh) for my application, and would last me about 20-30 mins. A fully charge Lipo has 8.4V, which drop to 7.2V in 5-10 mins and stabilize. All I need is to stepdown the voltage to 6V for my motors, and another 5V for circuit and control.

Since my supply voltage is considerably low and stable, switching regulator looks pretty promising.

The circuit would draw about 100-200mA only, I'm using LM317 for that. Worst case I'll be using 2x LM338.

You have good link/resource for switching? I reading a few here and there

Oh I thought the 10A is for battery charger, so it's to drive some motors, another project?

Hmm.. 8.4v-7.2v to 6v is not much difference. Wait, you sure it goes to 8.4v first? I thought rechargeable batteries output when loaded is pretty much constant, until it's charges fell below certain level, then it dips sharply. I was thinking a simple resistor might be enough. Then again there maybe other things to consider like motor EMF backlash, so using a pass transistor might be better like your high current regulator up there might be a good choice. Reason is, not much voltage drop so low heat dissipation required.

Well I remember I was reading these links some months ago SMPS and this SMPStech. Switching is nice, because can control the output voltage using a uC

Typical lipo output voltage during operation is 3.7V per cell. For complete charging, it require 4.2V, and usually a complete charge would give 4.25V. Off the charger, it would generally gives 4.2V. Upon load, it would drop gradually to 3.7V on the first 10% of discharge/usage. Thereafter, it would maintain at 3.7V until it reach 30% before it start dipping.

For NiMH, 1.2V is typical output voltage, while complete charge is usually 1.25V.

I'm using 2 Lipo cells in series, so that is would give typical 7.4V and 8.4V off charger. I have take care of all major motor related issue I have consider pass transistor, but isn't that the result same as regulator? A lot of power and heat dissipation?

I'm digging into buck converter and SMPS. I notice that it is normally use for regulating 24V to 12V, mostly more than 50%. My application of 8.4V to 6.0V looks like peanuts only Hopefully it can handle.

This post has been edited by Aurora: May 9 2009, 06:23 PM

Ah don't take everything I said to be correct, I just fired them off the top of my head

8.4v to 6v sounds very simple until you factor in the 10-15A current requirements
But I think that's where the fun is And I might need some advice in motor control from you later on

guys,how strong is the motor i need to make a electric go-kart??

This post has been edited by rokiroad: May 12 2009, 03:03 PM

It depends how fast and how powerful you want your go kart to be. For faster acceleration, you'll need a stronger motor. Seems like you will need a motor rated for few hp to be competitive enough. 1 hp = 745.7 watt. You will need motor with rating of several thousand watts. Try ask in go-kart thread (if any )

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Added on June 10, 2009, 10:45 pmI have reach the final stage of circuit prototyping, and will be moving on the the next step, which is PCB fabrication. Currently stuck on trace sizing. How wide should it be, for a 6v, 6A (typical) and 8A (peak) current? I googled around, and there are several version. I like to hear from someone who has experience it, if any.

Here's few sneak peek of the electronics:


The 2nd picture maybe familiar to some RC fan.

This post has been edited by Aurora: Jun 10 2009, 10:45 PM

guys..wanna ask..where can I get Solar Panel here in KL/Selangor? A specific shop. Any suggestion? Tq

How big of a sonal panel? There are shops at Jalan Pasar selling solar panel about the size of a wallet, I saw it last month. Not sure how much it cost. There are also some super big solar panel.

just a friendly reminder for those tinkering with lipos, make sure your device has a voltage cutoff or something similar to monitor and possibly cutoff your lipo once your pack reaches critical min voltage. You wouldn't want to burn down your home/office/car/friend's house etc etc

similarly, do not continue using damaged lipo packs (those that starts to bulge) and not to keep those damaged in-doors/near combustible items either.

Good point.. Actually charging is more dangerous than draining. Never leave Lipo charging unattended, while draining from Lipo, not encourage to overdrain. As soon as there is sign that battery is running flat, charge it immediately.

Those ppl is RC forum knows better in Lipo handling, because they use it on expensive equipment! heli and plane bah...

Reed (magnetic) switch? Is this part commonly available in jalan pasar?
http://en.wikipedia.org/wiki/File:Reed_switch_(aka).jpg
I need couple of this for replacement.

Hi,

I need to save my hardisk with a cytron PIC18F4580 learner board wich it have a RS232 port to connect to PC.

I'm just okay in electronic so i need some of you guy's help.

This is the link showing how its done:
http://sites.google.com/site/seagatefix/Home

So what i'm thinking of doing is to plug the TX from HDD to the RX and RX to TX.

So about the program part i'm not sure how to actually tell the PIC to take what it gets and send it to hyperterminal and receive from hyperterminal and send to the HDD.

This is roughly the programming that i can do in C:

#include <p18f4580>
#pragma config OSC=HS
#pragma config WDT=OFF
#pragma config LVP=OFF

void main ()
{
TRISCbits.TRISC6=1; \\output TX
TRISCbits.TRISC7=0; \\input RX these two is the TX and RX of the chip (from book, can i use any port if i wanted to?)

TXSTAbits.TXEN=1;
RCSTAbits.SPEN=1;

RCSTA=0x90; \\enable serial port and receiver
TXSTA=0x20; \\8 bit, low baudrate
SPBRG=7 \\xtal=20M, 38400

while(1)
{

if(PIR1bits.RCIF==0) \\i put this to seperate receiving and transmiting (tell me if its not nesssasary or its wrong)
{
while(PIR1bits.RCIF==0);
PORTBbits.RB6=RCREG;
}

if(PIR1bits.TXIF==0)
{
while(PIR1bits.TXIF==0);
TXREG=PORTBbits.RB7;
}

}
}

Argh its hard to type here when you can't tab!

If there's anything wrong or can be improved pls tell me.

Thanks in advance.

From the link all you need is a level translator to convert TTL to RS232 signal. You're attempting to use PIC because of some reason or for fun? And even if you use a PIC, you still need a level shifter.

Anyway I think you are trying to use the built-in hardware UART module plus a software UART. The problem is your software UART is non-existence.
Like this piece of code,
while(PIR1bits.RCIF==0);
PORTBbits.RB6=RCREG;

RCREG should contains a full byte of data received from the hardware UART.
You can't just assign them to pin6 of portb like that. You have to send out the individual bits in them one by one, AND watch the timing as you send them out or it'll end up as unreadable junk on the other end.