How Many Servos Can You Connect To A Ez-b V4 Wi-fi Robot Controller?

Question

Hi all. I am considering buying a 17 DOF kit from China, its ready with brackets. This kit can be used with 17 servos. Thanks.

Steve G · Answer

The EZ-B has 24 digital ports, so you can connect 24 servos. There is a way to daisy chain some servos but I don't have any experience doing that. If your going to use 17, then your ok and will have ports left over for other things if you wanted.

Robot Doc · Answer

The EZ-B v4 boasts 200mhz of 32-bit Processors (ARM Cortex M3 & Microchip PIC32) , 5 Volt Tolerant I/O, Energy Efficient Digital Switching Power Supply, Wi-Fi Connectivity with security, Embedded Web Server, Amplified Digital Audio with Speaker, 3 i2c ports, 3 x UARTs, 24 Multi-use Servo/Digital/Serial ports, 73 Servos (Dynamixel & PWM), 8 Analog ports, and Integrated Video... All packed in a mini 2.1" x 2.2" size!

Dunning-Kruger · Answer

Further each digital port can handle 5amp max, total 20amp at once before the main fuse blows...

Leaderone · Answer

Dang! I was reading and reading but did not see the "24 Multi-use Servo....." Thanks for pointing that out! Thanks both! I have been reading me up on this subject now for 1 month. My approach now will to buy the shell from Alibaba and by luck I found an article about EZ. Wish me luck:)

Leaderone · Answer

Thanks for advice RR! Next question: should I buy my robot kit complete with servos or not.

Robot Doc · Answer

You have to be careful when buying servos for different applications (robots). The servos come in different sizes and shapes. You might want to purchase the servos that the kit was designed to use.

CochranRobotics · Answer

The thing to know/remember is that the digital ports are unregulated. if you are going to power your bot with 7.2Volts, make sure your servos can handle 7.2 volts, or regulate the power off of the ports between the servos and the ez-b.

Jeremie · Answer

@RR, @Leaderone The ez-bv4 can handle 5A continuous current draw total, up to 20A spiked current. Servos do not actually draw all that much current until they are stalled or a number of them are being used at the exact same time. In most applications of 24 servos all the servos are not being moved at the same time.

Leaderone · Answer

Thanks again all. So much to learn. But I need a hobby. I will get the kit with the servos and build it from there. Now I need to find a good power source. In the sales post they state I have to buy a "HM battery X 1" because they can't ship it. I guess they think about "MH" battery.

Dunning-Kruger · Answer

@Jeremie... Thanks dude... @Leaderone You should buy a lipo or niMh for your power needs...

Dunning-Kruger · Answer

@Anthony ... Which fuse?... poly or main fuse? I don't think that is correct (or oversimplifying things), Anthony... I have pulled way more than 5amps ( a burst or two) threw the ezb board without tripping the poly or burning out the main fuse... Remember what Jeremie said... 5amps continuous with 20 amp bursts.... I don't think you'll burn the main fuse drawing 5amps, since it is a 20amp fuse... Here's the manual for the ezb4 EZB4 Data sheet

Dunning-Kruger · Answer

I think what you referred to as "freaked out" and resetting was due to power supply issues... Your battery couldn't provide enough current so your ezb reset... it is a classic power issue... So I am willing to bet your ezb reset due to an under volt situation and not because the poly fuse was tripped... Once I tripped the poly fuse (because of 5 locked servos), my ezb did not reset (I was using a 10amp niMh D cell pack)... All that happened was the ezb4 stopped responding... servos would not move nor did the digital ports respond... Powering it off for a few minutes reset the poly fuse and all was normal after that...

Jeremie · Answer

@RR is correct, the main automotive blade fuse is rated for 20Amps. I suspect the issue might be the brand HDservo. I have never used that brand and have have no experience with them. I'm guessing they draw quite a bit of current which Anthony's power supply, wiring, or connectors possibly cannot handle and it's browning out the ez-b. I could be mistaken but If we could get a sample servo I could do some tests.

Jeremie · Answer

I also have a variable bench top power supply that is rated for 10A and it also will brown out when trying to power over 8 servos at the same time. This is because of in-rush current. You will not see it because it's so quick but the servos are demanding more than 10Amps in a burst, the voltage then drops to try and keep up, at that moment the voltage goes so low that the ez-b resets.

CochranRobotics · Answer

The 6 has 12 servos and runs off of a 7.4 v lipo. It can move all servos at the same time. It does this when starting from its "legs closed" position and going to the stand position. These are all HD servos. All of the power is coming from the ez-b. If you were to do a lot of movement, you might want to power off of an external power source. I have not had the issue you are having with any of my 8 ez-b v4's. To be fair, one of them has the servos being powered from a different supply due to brown out issues I was having and to provide some components with 5v, some with 6v and some with 7v. The side effect of this is that it allows me to power the devices off of multiple battery packs, but I haven't had the poly fuse flip on me an any of the robots.

CochranRobotics · Answer

Took me a while to type that on my phone. Caused me to miss Jeremy reply.

Jeremie · Answer

Thanks @d.cochran, I forgot that I probably should have mentioned that I have run Six with 18 servos from a 7.4V lipo without any brownouts, this is because LiPo batteries can provide the in-rush current that the servos demand.

The difference is that switching power supplies, or even linear voltage regulators, have a very hard time meeting the burst current demands of multiple servos which is often over 10Amps. This was one of the largest reasons we are now using LiPo batteries connected directly to the servos (Fuse protected of course) as opposed to using voltage regulators.

Dunning-Kruger · Answer

@Anthony... (read Jeremie's last few posts)... 10amp power supply can't handle the initial inrush of power that those servos require... We have been through this before in another thread about your power supply (a while back) not handling the initial inrush need to start servos moving.... Again, what you experienced was a brown out that triggered the ezb reset... Minimum power supply should be 20amps in my opinion...

For my inMoov project I am looking at a 60 or 100amp power supply....

Leaderone

How Many Servos Can You Connect To A Ez-B V4 Wi-Fi Robot Controller?

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