Hi, i'm new in using LiPo batteries. After reading and watching videos i have some questions.
I'm trying to build a rc car that'll carry something. Because of this i need to use 2 servomotors to allow it to move. After choosing servos with right torque for my project i saw on datasheet the stall current that is 1A (6V). My four AA battery pack can't provide such current and the servos doesn't work.
My idea is to use a lipo battery (i found the right one for my project. Is a 2S 7.4V 5000mAh) but now i'm not sure how to proceed.
For charging i'm planning to buy a LiPo charger to prevent overcharge.
To preventing overdischarge i'm planning to put a IC buzzer that check if one cell is below the minimum. On the internet there are some BMS but i have to solder it to battery (battery has XT90 connector) and some images shows B+, B- and BM pins on BMS. I don't know what BM is and what i should solder on it.
Someone knows IC cutoff protection circuit? If i pay attention i could go on with only the buzzer?
Another question is: i want to solder all wires on a pcb because breadboard can't hold up such current and because i need something more stable. Is possible to solder battery wires (LiPo > XT90 Connector M/F > Wires) directly on pcb to power servos and arduino, antenna etc? (Obviously everything with proper voltage (step-down converters)
Thanks a lot!
(If someone has a suggestion on a book regarding batteries and powering methods is welcom)
Soldering is preferable. Protoboard is an easy option.
Keep the motor currents away from controller power and signals.
If You could grab pen and paper showing what You intend to build the replies will be more usefull, not guesses or misunderstandings that takes time to sort out.
Exactly! Thanks!
You likely have signal cables to the servos.... No bother.
You show an UNO and it will barely run from 7.4 volt. I'm not sure if the spec for min Vin is 7.0 or 7.5. The voltage will drop as the motors download the battery.
Summing it up: It looks good, no smoke generated. A separate battery for the UNO would increase run time before charging, or a step down to 5 volt fed into the UNO 5 volt pin.
Yes, there are signal cables but i didn't show that on the picture.
Because the servos can provide the right torque only at 6V (at 4.5V torque is not enough high to move the car) maybe to have a "longer life" before the charging i can put a 3S Lipo instead of 2S.
Then i can connect as you mentioned a stepdown to obtain 6V, than connect in parallel servos and another stepdown to obtain 5V and fed arduino trough 5V pin. Or maybe i could fed 11.1V on Vin arduino (6-20V are allowed on Vin) and use only one stepdown to 6V for servos.
What do you think?
Talking about servos, i need to put something to prevent reverse current?
Is better use of battery energy to have a step down to 5 volt for the UNO, the ultra sonics, and, I guess, the remote receiver. For an UNO 6 volt Vin will not work and the built in 5 volt converter just manage the UNO and maybe 1 or 2 LED. If the RC device does any transmitting it will not work. The ultrasonis need current for the pulse.
Usin 2 step downs, one for 6 volt and one for 5, a 2 cell LiPo will work but of course 3 cells will keep things running longer before charging the cells.
Servo driver board is mandatory if i have 2 servos? I saw a lot of project using some of this driver board but i can easily control them trough their signal wire. I'm a little bit confused.
Servomotor deals with noise problems? I need to put electrolitic capacitors to isolate my arduino?
Those servos have one cable for the pulsing signal and it connects to a digital output pin. The next servo signal pin is connected to its own digital output. No need for extra circuitry.
Adding a 100 uF cap is never wrong. Connect them between servo power plus and servo negative. Connect servo negative and controller GND.
