A Hobbico Quick Field Charger MkII for NiCad, NiMh, and LiPo packs
A Schumacher SEM-1562A for 6 v and 12 v lead acid batteries.(Kiddie car and UPS batteries)
What to buy would depend on your robot, and its environment. Outdoor robots might be larger and tend towards Gel-call batteries, so that type of charger would be good. Indoor bots would more likely run on packs of NiMh or LiPos. I prefer getting a charger that covers several types of batteries if possible. Battlebots/Robot Wars folks went into more expensive chargers that perform very well on larger packs, like the Astroflight 112D.
Another battery I've considered has been the A123 systems battereis, that I believe can be charged with LiPo chargers.
One thing to remember, charging LeadAcid or LiPos probably needs to be outside, away from burnable structures, as it is fairly easy to have a minor mistake turn into a big fire.
You want NIMH batteries, they hold more charge, are not affected from memory effect and current technologies can surpast the current outputs of NICaD batteries.
Another advantage of rechargables is that 4 of them gives 4.8V, whereas 4 alkalines gives 6V. Also, where alkalines tend to slowly drop in voltage, rechargables tend to maintain their voltage unti the stop alltogether!
I know this is true of NiCds. Can anyone confirm the voltage /discharge curve for NiMH?
A major disadvantages can be seen when you make a mistake. If you short circuit a NiCd, your wires heat up and the insulation melts and it frightens you half to death.
I'm too yeller to use rechargables, so I use el-cheapo alkalines.
There are two exceptions. I once found a cheap source of 7.2V Tamiya racing packs which are NiCd. The other is that I use a lead acid batttery with Big Chaser.
well i'm using 4 standard rechargeable AA batteries for my current robot (that eats 5V), but the next one will require 12V. I've seen a NiMH battery pack on many sites that come for around 25 €, but the recharger alone costs 70 €! I was even considering a scooter battery (as you can read in the shoutbox), since my new robot would be quite big anyway. It costs like hell but at least should provide plenty of energy :) Btw, can i just connect one of those to say, arduino? It requires 12V just like the batteries, but maybe the amperage will kill the board?
Amperage won't kill the board. The board will only draw the current it needs. Voltage will kill the board. I don't know what the standard drive voltage for arduino is, but If it's 5V, you'll need a 7805 regulator. Be aware that I separated my motorcycle battery from my MCU and run the MCU off a seperate battery as the power drain on the battery when the motors were starting up was resetting te PIC.
My battery cost $40 and the charger was $10.
Ask questions. Don't fry your hardware. Unless you're a cousin of Frits.
Yup, the Arduino board (at least the Diecimilla) has an onboard voltage regulator, so you can feed it anywhere between 7-12v comfortably. It should be fine from a motorcycle battery, but as BoA says, if you're powering big motor with the battery too, they may cause it to sag enough to cause your Arduino to reset. You can stick a capacitor across its input leads to help minimize that problem, or just stick it on a smaller separate battery to be sure it won't affect you.
Thanks guys, you were very helpful! This sure is a friendly forum :)
I really should take some times to study/refresh the basics of electronics.. Anyway, that thing about resetting the arduino looks important. I don't want to have another set of batteries for the board, so i think i could do with the capacitor. I even have some vague idea of what a capacitor is :) No ok, is it too much to ask how to mount it? Or what kind of capacitor i need?
For the power input, I'd use about a 10 uF electrolytic capacitor. That's the kind that looks like a barrel, and both leads come out of the same side, and one of them is longer than the other (it's polarized). You also want to be sure that it's rated for well above whatever voltage you're going to be feeding it. If it's going to be connected to a 12v battery, then a 35v capacitor would do nicely. Something like this. It doesn't hurt to go bigger -- this 22uF one would work fine too. A bigger capacitor will let your circuit endure longer voltage dips without a problem. Someone can correct me if I'm wrong, but I think the only downside of a bigger capacitor is that it costs more and takes up more space (and, as I've learned, it makes a bigger bang if you accidentally hook it up backwards :)
As for how to hook it up, the capacitor should be connected BEFORE the onboard voltage regulator, so you want to connect the negative lead of the capacitor to the Arduino's Ground, and the positive lead of the capacitor to the Arduino's Vin pin (which is connected to the barrel power connector). You could also connect the capacitor across your power wires before they reach the Arduino, if that's more convenient. Just try to get it as close to the Arduino as possible. And be SURE not to wire it backwards :) The side of the capacitor with the stripe down the side and the shorter lead is negative.
Great explanation CowGod :) Many thanks.. I'm making an order on sparkfun, they have 10uF 25V capacitor or 100uF 25V capacitor (btw, they are decoupling, is it ok?).. I'm buyng a couple of them anyway, they're very cheap. Do you think 25V can be enought for a 12V power ? or 35V is better? I can always go and buy them at the local electronics shop :)
Ok i'll be sure to hook up the right side.. so the shorter lead is positive, right? BOOOM :D
Whoa, Sparkfun redesigned their site. Yeah, 25v should be fine. Car/motorcycle batteries can get up to about 15v when the motor is running, and you'd want to have a few volts on top of that for random spikes. I wouldn't use anything less than 20v, but 25v should be plenty of cushion. Especially since it sounds like yours won't actually be in a circuit with an alternator, right? So yeah, 25v is fine. And 'decoupling' refers precisely to this kind of usage -- decoupling your power input from the battery so that you aren't affected by sags and spikes in the battery's output. It's kind of like a little tiny UPS for your Arduino that only holds 0.5 second's worth of charge :)
Not on the inputs. If you put it on the input (even physicall close to the input) then a rapid switch on of your motor will still draw from the cap. You need a bit cap on the 5V side of the regulator. The board might already include on. I'm fascianted by the notion of a cap on teh 12V side (I've seen it on the data sheet for the 7805) but I don't see why ot would work...
Aye, I've always seen it recommended to use caps on both sides of a voltage regulator -- the numbers I remember reading were around 10uF on the input side, and about 1uF on the output side. But since the voltage regulator is onboard the Arduino, I assume it's got a cap on the output side already. I haven't looked at the schematic, but I know there's several SMT caps on the board. Hell, it might actually have one on the input side already too, but it doesn't hurt to add another one just off the board.
edit: yup, I checked the Arduino schematic and it's already got 100uF capacitors on either side of the voltage regulator. Here's that section of the schematic:
Today i casually visited a local shop of RC radio and modelism and i found they also sell many batteries! yay! :)
They have NIMH pack with 7 V (7.3 iirc) and also some lead 12V square batteries that looks almost like scooter batteries but a bit smaller, they came for 20€ which is not bad, and 19€ for the charger. I was almost sure to buy it before i read your post :P I'll go again on monday and ask some more info..
Btw they have some fine goodies, such as a great choice of servo, some remote controller, motors (no geared asfar as i saw) some ubercool RC elicopter (for 400€ ),RC fuel powered cars, etc etc. I definitely return to take a second look :)
Small collection
A GWS-MC2002 for multiple NiCad or NiMh packs.
A Hobbico Quick Field Charger MkII for NiCad, NiMh, and LiPo packs
A Schumacher SEM-1562A for 6 v and 12 v lead acid batteries.(Kiddie car and UPS batteries)
What to buy would depend on your robot, and its environment. Outdoor robots might be larger and tend towards Gel-call batteries, so that type of charger would be good. Indoor bots would more likely run on packs of NiMh or LiPos. I prefer getting a charger that covers several types of batteries if possible. Battlebots/Robot Wars folks went into more expensive chargers that perform very well on larger packs, like the Astroflight 112D.
Another battery I've considered has been the A123 systems battereis, that I believe can be charged with LiPo chargers.
One thing to remember, charging LeadAcid or LiPos probably needs to be outside, away from burnable structures, as it is fairly easy to have a minor mistake turn into a big fire.
You want NIMH batteries,
Voltages
Another advantage of rechargables is that 4 of them gives 4.8V, whereas 4 alkalines gives 6V. Also, where alkalines tend to slowly drop in voltage, rechargables tend to maintain their voltage unti the stop alltogether!
I know this is true of NiCds. Can anyone confirm the voltage /discharge curve for NiMH?
A major disadvantages can be seen when you make a mistake. If you short circuit a NiCd, your wires heat up and the insulation melts and it frightens you half to death.
I'm too yeller to use rechargables, so I use el-cheapo alkalines.
There are two exceptions. I once found a cheap source of 7.2V Tamiya racing packs which are NiCd. The other is that I use a lead acid batttery with Big Chaser.
well i'm using 4 standard
well i'm using 4 standard rechargeable AA batteries for my current robot (that eats 5V), but the next one will require 12V. I've seen a NiMH battery pack on many sites that come for around 25 €, but the recharger alone costs 70 €! I was even considering a scooter battery (as you can read in the shoutbox), since my new robot would be quite big anyway. It costs like hell but at least should provide plenty of energy :) Btw, can i just connect one of those to say, arduino? It requires 12V just like the batteries, but maybe the amperage will kill the board?
So many doubts, so few certainties :)
Amps, Volts and Ohms
Amperage won't kill the board. The board will only draw the current it needs. Voltage will kill the board. I don't know what the standard drive voltage for arduino is, but If it's 5V, you'll need a 7805 regulator. Be aware that I separated my motorcycle battery from my MCU and run the MCU off a seperate battery as the power drain on the battery when the motors were starting up was resetting te PIC.
My battery cost $40 and the charger was $10.
Ask questions. Don't fry your hardware. Unless you're a cousin of Frits.
Yup, the Arduino board (at
Yup, the Arduino board (at least the Diecimilla) has an onboard voltage regulator, so you can feed it anywhere between 7-12v comfortably. It should be fine from a motorcycle battery, but as BoA says, if you're powering big motor with the battery too, they may cause it to sag enough to cause your Arduino to reset. You can stick a capacitor across its input leads to help minimize that problem, or just stick it on a smaller separate battery to be sure it won't affect you.
Dan
Thanks guys, you were very
Thanks guys, you were very helpful! This sure is a friendly forum :)
I really should take some times to study/refresh the basics of electronics.. Anyway, that thing about resetting the arduino looks important. I don't want to have another set of batteries for the board, so i think i could do with the capacitor. I even have some vague idea of what a capacitor is :) No ok, is it too much to ask how to mount it? Or what kind of capacitor i need?
Thanks again :)
For the power input, I'd use
For the power input, I'd use about a 10 uF electrolytic capacitor. That's the kind that looks like a barrel, and both leads come out of the same side, and one of them is longer than the other (it's polarized). You also want to be sure that it's rated for well above whatever voltage you're going to be feeding it. If it's going to be connected to a 12v battery, then a 35v capacitor would do nicely. Something like this. It doesn't hurt to go bigger -- this 22uF one would work fine too. A bigger capacitor will let your circuit endure longer voltage dips without a problem. Someone can correct me if I'm wrong, but I think the only downside of a bigger capacitor is that it costs more and takes up more space (and, as I've learned, it makes a bigger bang if you accidentally hook it up backwards :)
As for how to hook it up, the capacitor should be connected BEFORE the onboard voltage regulator, so you want to connect the negative lead of the capacitor to the Arduino's Ground, and the positive lead of the capacitor to the Arduino's Vin pin (which is connected to the barrel power connector). You could also connect the capacitor across your power wires before they reach the Arduino, if that's more convenient. Just try to get it as close to the Arduino as possible. And be SURE not to wire it backwards :) The side of the capacitor with the stripe down the side and the shorter lead is negative.
Dan
Great explanation CowGod :)
Great explanation CowGod :) Many thanks.. I'm making an order on sparkfun, they have 10uF 25V capacitor or 100uF 25V capacitor (btw, they are decoupling, is it ok?).. I'm buyng a couple of them anyway, they're very cheap. Do you think 25V can be enought for a 12V power ? or 35V is better? I can always go and buy them at the local electronics shop :)
Ok i'll be sure to hook up the right side.. so the shorter lead is positive, right? BOOOM :D
Whoa, Sparkfun redesigned
Whoa, Sparkfun redesigned their site. Yeah, 25v should be fine. Car/motorcycle batteries can get up to about 15v when the motor is running, and you'd want to have a few volts on top of that for random spikes. I wouldn't use anything less than 20v, but 25v should be plenty of cushion. Especially since it sounds like yours won't actually be in a circuit with an alternator, right? So yeah, 25v is fine. And 'decoupling' refers precisely to this kind of usage -- decoupling your power input from the battery so that you aren't affected by sags and spikes in the battery's output. It's kind of like a little tiny UPS for your Arduino that only holds 0.5 second's worth of charge :)
Dan
Nah!
Not on the inputs. If you put it on the input (even physicall close to the input) then a rapid switch on of your motor will still draw from the cap. You need a bit cap on the 5V side of the regulator. The board might already include on. I'm fascianted by the notion of a cap on teh 12V side (I've seen it on the data sheet for the 7805) but I don't see why ot would work...
...can anyone help?
Aye, I've always seen it
Aye, I've always seen it recommended to use caps on both sides of a voltage regulator -- the numbers I remember reading were around 10uF on the input side, and about 1uF on the output side. But since the voltage regulator is onboard the Arduino, I assume it's got a cap on the output side already. I haven't looked at the schematic, but I know there's several SMT caps on the board. Hell, it might actually have one on the input side already too, but it doesn't hurt to add another one just off the board.
edit: yup, I checked the Arduino schematic and it's already got 100uF capacitors on either side of the voltage regulator. Here's that section of the schematic:
Dan
good, some work saved :)
Three advices:1) Get many
Three advices:
1) Get many batteries, and get many of the same kind
2) Get batteries with as many MhA's as possible
3) Get 2 rechargers, or another setup, so you can charge at least 8 at a time
That will make you happy!
Heres my advise on top of
Heres my advise on top of frits
Dont listen to frits about hardware :p
NIMH batteries are now cheaper and have one of the highest power densities (LiPo-Lion-NIMH-NIcad-Alkaline-Lead Acid)
Put out a lot of current as compared to size and new NIMH technologies allow for batteries to be able to draw 30+ amps at a time
Get battery holder, not necessarily premade packs. This allows you to reconfigure your batteries. I myself have about 40 NIMH batteries :)
You can put tape over battery holders if it makes you feel better.
here is an example: You can
You can take the batteries out that you put in. THis also allows you to buy a cheap wall charger too.
uhm that sounds nice.. Today
uhm that sounds nice..
Today i casually visited a local shop of RC radio and modelism and i found they also sell many batteries! yay! :)
They have NIMH pack with 7 V (7.3 iirc) and also some lead 12V square batteries that looks almost like scooter batteries but a bit smaller, they came for 20€ which is not bad, and 19€ for the charger. I was almost sure to buy it before i read your post :P I'll go again on monday and ask some more info..
Btw they have some fine goodies, such as a great choice of servo, some remote controller, motors (no geared asfar as i saw) some ubercool RC elicopter (for 400€ ),RC fuel powered cars, etc etc. I definitely return to take a second look :)