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Topic: Need Advice on MotorShield - Shoot your suggestions!!!! (Read 1 time) previous topic - next topic

couka


The motors will be driven by a dual H-Bridge motor-shield via arduino and
I planned to use a step-down buck that converts the 12v to 6v to powerup the uno or pro-mini. But I didn't know the spikes will affect the board. So, Do I need to add a 470 or 570uf ? Please advice.
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There should be caps of a few 100µF, your arduino is probably fine, if the motors are connected to the 12V side.

The battery you posted probably works, but note that the capacity is actually only about 2200-2300mAh (and the usable capacity is even lower, since it seems to cut-off at 3.6V) and the charger... well I would not let it charge unsupervised. Really.


lg, couka
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rshnk90

Quote
There should be caps of a few 100µF
Can you let me know where this should be exactly placed, to the motor points itself or arduino pins ?


As for the battery, You mean 2200-2300mah is good enough to run all the parts and no need for 6800mah ?

If no, do you have any other suggestions for the battery ( maybe a link to the product itself would be nice to have a look )


Thanks Couka!!

raschemmel

I said "wait and see" because there is no way to know in advance if the Buck converter will filter the spikes until you actually try it. For the samereason, no one can know how many uF to use until you try it. 100 uF may not be enough. As far as WHERE to put the caps ?
Thar's simple, on the input and output of Buck converter.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

rshnk90

Thanks Raschemmel, I will try starting with 100-200uf and see how it goes.

By the way, Im still confused at what power source would be better in terms of size and weight. I'm trying to keep it small as much as possible with sacrificing little weight ( since im using high-torque motor )

So, 3.7v 2600mAH x 4 (cells) = 14.8v / 10.4AH  Is this a good choice to power the 2 x 12V motors + all other components ? cause I'm worried.. about 14.8v if it would damage the motors.

and instead of 4, If I use 2 cells.. it is 7.4v which is lower than the required current. but use a boost convertor for 12v ?

Any ideas and suggestions for this ?

raschemmel

#19
May 21, 2016, 09:41 pm Last Edit: May 21, 2016, 09:53 pm by raschemmel
FYI, since you seem to be new to Lipos,
Quote
Most LiPo/Lion cells are 3.7V nominal (4.2V max and 3.2V min), so a 4S pack should go up to 4*4.2V = 16.8V at full charge and go down to no less than 4*3.2V = 12.8V at full discharge.Oct 14, 2012
Quote
Is this a good choice to power the 2 x 12V motors + all other components ? cause I'm worried.. about 14.8v if it would damage the motors.
NO.
Use 3S (12.54 V at full charge, can be as low as 3*3.2V = 10.7V).
Not a good idea to overvolt the motors. If you were using some kind of closed loop feedback you could regulate the voltage using the PWM duty cycle. I haven't seen any vendors link for you motor shield so I can't comment on that. In fact , I haven't seen anything from you on how you actually plan to control the motors. No mosfet part numbers , no code, nothing. It is way to early to talk about controlling the voltage of a system that hasn't even been designed yet. As far as I can tell, you have the cart before the horse. Where I work, they design the system, have engineering design reviews,
finalize the design, then order parts. I don't know where you learned electronics but they must do things backwards there. Sorry if that doesn't sound too complimentary but I call it as I see it.
Post a schematic of your system and then we'll talk. Here on the forum , we do things the professional way. You may be a hobbyist, but we are electronics professionals, not hobbyists. We start with a feasability study or a preliminary design and refine it from there. The schematic is introduced early on, if only in a block diagram and then a real schematic. The code should start with an algorithm, and then progress to actual code. We don't just throw stuff together and turn on the power. That's what hobbyists  do, which explains why they wind up here asking for help.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

rshnk90

FYI, since you seem to be new to Lipos,
True, I'm new to this and thanks for clarifying the volt. I'm still concerned about the space, Can I use 2 x 4.2v (aka 3.7v) cells and use a boost converter for 12v ?

Is that advisable to do ?

raschemmel

Quote
Can I use 2 x 4.2v (aka 3.7v) cells and use a boost converter for 12v ?

Is that advisable to do ? 
Based on your specs of 120 mA/per motor, something like this could work.

You need to remember that you will have to do system level testing to fine tune the filter cap values.
You should not be shopping for motors without shopping for motor driving mosfets or a motor shield at the same time. One should be chosen to match the other.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

rshnk90

I tried putting it to cart and they charge more for the shipping than the product itself. $10.78 ( excluding 3.99 ) outside US.

So, I tried to find the same on eBay, but I came up with something similar like this

http://www.ebay.com/itm/5pcs-2A-DC-DC-2V-24V-Step-up-boost-Power-supply-Converter-Module-/201577598458?hash=item2eeef60dfa:g:scoAAOSwf-VWXV4p

or

http://www.ebay.com/itm/2pcs-DC-DC-Adjustable-Step-up-Power-Converter-Module-XL6009-M17-/301723389663?

Does that work too ?

raschemmel

#23
May 21, 2016, 11:28 pm Last Edit: May 21, 2016, 11:32 pm by raschemmel
Looks like it would work .
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

rshnk90

Looks like it would work if the input voltage is < 8 V.
I guess the second link wont fit ? Since my volt will be 4.2 x 2 = 8.4V

What about the 1st link, it doesn't say anything like that

Maximum output current: 2A
Input Voltage: 2V-24V
Maximum output Voltage: greater than 28V

So think that might work ?

raschemmel

#25
May 21, 2016, 11:39 pm Last Edit: May 21, 2016, 11:41 pm by raschemmel
That's incorrect.

Input voltage is 5V < 8 V  so it is fine.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

rshnk90

That's incorrect.

Input voltage is 5V < 8 V  so it is fine.
But that is  4.2volt each cell. If I use 2 cell it's 8.4 right ? correct me again please.

raschemmel

The boost converter input voltage range is 5V dc to 32 Vdc.
The battery voltage falls in that range. There is nothing else to discuss.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

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