Secondary Circuit Protection

Help & Support Robot Parts
1

Hi,
We are working on a project involving mobile robot and we need to power 4DC motors with 12V,5.5A each.Now the best possible option seemed to be to use LiPo or Li ion rechargeable batteries. It was suggested to us that a secondary circuit protection is needed for the lithium batteries apart from the protection already present.Is it necessary to have a secondary circuit protection and is the protection circuitry readily available in the market or should be designed separately? .We are all newbies and hence any feedback is appreciated.

Thanks.

2

Hi,

It all depends on what you want to do, like for example, if you want to have a charger on board. LiPo batteries are still pretty dangerous so having a protection circuit is a good Idea. If you plan to have the option to run the robot on the battery or using an external power supply, you should definitely have some kind of protection to make sure your external power supply will not apply voltage directly on your batteries (Usually a basic Diode circuit will do). We don’t have any Stand alone protection circuit. Some shield or motor controllers may have protection but it is a case-by-case and some research will be required to see if they have.
Best regards,

3

Hi,
Thanks for taking your time to reply. I got a PCB online(link attached). Can you suggest us if it works? Also can you advice us whether to use a separate power source for electronic components and motors of a robot or is a single power source is enough?

Thanks

link:
all-battery.com/protectionci … 32010.aspx

4

Hi,

For the protection circuit, you should contact the company directly, they should be able to give you advice on their products.

We cannot tell for your design if it would be enough as we don’t have all the details, but usually it is OK to use a single power source if it is powerful enough.

Sincerely,

5

Hi,
In a mobile robot can you suggest whether a buck converter can be used in place of a voltage regulator?We have a 12V,30A SMPS and and we need 24V,0.5A for electromagnetic locks.Can a boost converter be used? Also, is there any circuit which can be designed to safely switch off the power supply when not in use?

Thanks.

6

Hi,

There should not be any problem in using buck converters. Just make sure it can supply the required current.

You should probably look for a switch system on the 12V after the power supply rather than switching the power supply off. If you really want/need to turn the power supply off, you can use a switch made for 120V ( 230 if you are in Europe) but it needs to be done properly or it can be dangerous.

Best regards,

7

Hi,
Can you suggest some general precautions taken while constructing a mobile robot?

Thanks.

8

Also i have a 12V,30A SMPS and for the boost converter it should be dropped to 4A with voltage ranging from 5V-32V. Can I use a power resistor with rating 4.7ohm and 10W? If not , can you suggest a method to reduce the current?

Thanks

9

Hi,

You should always be careful if you plan on playing with high voltages and high current.

We are sorry but we don’t understand how you are planning to connect everything together and what your goal is with the 4.7Ohms resistor. The buck converter can supply a maximum of 4A, you don’t have to limit its input to 4A if this is what you were trying to do.

Best regards,

10

Hi,
Basically we want to create a battery backup for the electronics part of the robot as shown in the image below. Instead of 14V adapter, we are using 12V,30A SMPS and increasing its voltage to 14V by boost converter. In the data sheet of the boost converter, it was given that the maximum input current is 4A. Hence we are using power resistors to limit the flow of current. We have 4.7ohm and 10W power resistor. Is it sufficient or some other resistors are required? Can you please tell if something is wrong in what we are trying to do.
Also the battery is LiPo which is directly charged from the mains by an adapter.

Thanks.

arduinoback-up_m.jpg
arduinoback-up_m.jpg1020×576 64.8 KB

11

Hi,

Please note that we cannot do validation of designs, but only offer general guidelines.

The power consumption after the regulator will dictate the input current. The resistor approach is not a solution, it will drop you voltage and will not limit the current like you intend it to.

Be careful, LiPo batteries require to use a good LiPo charger or else there is a lot of risk of the battery bursting into flames. You will probably also need a special circuit if you plan charging the battery when plugged into the circuit.

Best regards,

12

Hi,
Then in what way the current can be limited to 4A? Also as the boost converter works in the range 3-22V, the drop in voltage is not a problem.

Thanks

13

Hi,

The way to limit the current is by making sure your powered circuit current draw is below the converted current value at the output. You do not need a circuit to limit the current.

Best regards,

14

Hi,
For my project ,we want to provide power to the arduino uno by external power supply. We have brought down the voltage to 12V,30A by SMPS.What current ratings should be considered. As in what is the maximum current that can be allowed through the arduino without burning it out? At what pins should the power supply be connected?

Thanks

15

Hi,

Check the datasheet of the regulator to know what is the maximum output current. Your Arduino and peripherals should not use more than that.

The power supply should connect to Vin or the barrel connector.

Best regards,

16

Hi,
Can you suggest us the best way to have a battery backup for Beagle bone black? We will provide a power supply from the USB but we need a battery backup. And also at what pinss the backup should be provided.

Thanks
.

17

Hi,

The battery pins information can be found in the manual
https://www.element14.com/servlet/JiveServlet/downloadImage/38-12793-170081/bbb-batt-srm.jpg"%20alt="bbb-batt-srm.jpg
You can check on the manufacturer’s website for more information on how to do this: goo.gl/5lGHyA

Best regards,

18

Hi,
Isn’t there any other way? We would like to provide a 5V battery backup from the jack port which is adjacent to the adapter socket. Is it alright or does it damage the board? What is the tolerance of ths jackport. I mean what is the minimum and maximum voltage that can be suppliedto the jack without damaging the BBB.

Thanks.

19

I think you need to contact that company from where you buy this product. Because they will guide you properly.

20

Hi,

As daljitgroup mentionned, contacting the company directly may be a good Idea.

The jack was not meant for a rechargeable battery but it can be possible to use it but will not be able to charge the battery via the barrel. According to the datasheet, the input voltage can go up to 20V
ti.com/lit/ds/symlink/tps65217.pdf

Best regards,