17 servo project is going crazy

Hello, I am working on a 17 servo biped robot and all of my servos are going haywire. I am using an Arduino Uno with a servo shield I made myself. My servos are small 4.8-6 volt hobby servos. I have separate power supplies for the Arduino and servos and I have capacitors to smooth out the sudden draws from servos. In my sketch when I have 3 or more servos trying to move all my servos will start going crazy. This only happens when I have more than six servos plugged in. Does any one know how to fix this? I've been searching the internet and can not seem to find an answer that works. Would adding diodes to the power and signal going to each servo help?

I am using an Arduino Uno with a servo shield I made myself

I'd contact the manufacturer if I were you.

Hi and welcome.

Servos need a lot of power. Adding an extra capacitor will not help to fix an insufficient power supply. Get info on the servos in use, and make sure your power supply and print layout can handle way more than the sum of the currents of all servos connected to your shield.

If you still need help, tell all about that shield of yours. Leaving that out, means no one can assist you unless they have a set of at least a crystal ball and a magic wand.

You'd need farads of capacitance to fix this issue!! - get a 10 to 20A power supply if you want to run lots of servos like this.

We are talking perhaps 1A peak per servo, and even 100,000uF will give marginal help at high current low voltage loads. A proper supply is the right approach.

People always seem to underestimate the power requirements of motors and servos, since they are several orders of magnitude more than most other electronic devices.

MarkT: get a 10 to 20A power supply if you want to run lots of servos like this.

I have to run the robot on batteries, is there batteries that would give me that high amperage?

MAS3: tell all about that shield of yours.

Sorry, I forgot about that the first time. My shield has all 17 servo pins and my capacitors wired together in parallel with power to my 6 volt battery pack (four AA) and grounding both to that battery and the board. The signal wires each got to their own port I'm using ports 2-13 and A0-A4. I am currently running my Arduino from a 9volt battery to the voltage in spot on the board. I'll put a picture of my board up later.

Thanks for all the help.

Sprint44: I have to run the robot on batteries, is there batteries that would give me that high amperage?

Re-chargeable batteries can usually provide plenty of amps. Of course if the capacity (amp-hrs) is low the charge will be used up very quickly.

Trying to power 17 servos from 4 x AA NiMh cells seems to be asking too much - they might be sufficient for a few minutes after they have been fully charged. Use much larger cells Or maybe a pack of 4 x AA cells for every 3 servos.

A lot depends on how long you want the batteries to last between charges.

Separately, a PP3 style 9v battery is not really suitable for powering the Arduino. Use a pack of 6 xAA cells

...R

Hi,

My shield has all 17 servo pins and my capacitors wired together in parallel with power to my 6 volt battery pack (four AA)

You are lucky to get 3 servos to run with AA batteries. You need Lipo or Seal Lead Acid to power them.

The 9V battery is not one of these? They are only suitable for DMMs and smoke detectors not Arduino. What type of servo, post link to spec/data please?

If you are not moving a servo and if the servo shaft is undergoing an applied load torque, it will still consume current to keep the position it has been set at.

Have you checked you AA battery voltage while moving or even having your servos at "rest"?

Thanks.. Tom.. :)

The servos are these: https://www.radioshack.com/products/radioshack-micro-servo

I haven't checked the voltage with all the servos running yet, I'll do that tonight. I'm currently using alkaline batteries because that is what I had I am willing/planning to get something rechargeable.

Thanks for all the help I'm still new to electronics and my teacher is at a loss on what to do.

Here are the pictures of my servo shield.

Sprint44:

Here are the pictures of my servo shield.

Try again.

.

larryd: Try again.

What do you mean by that?

Post your images as discussed here:

Here is my servo shield.

IMG_1280p.jpg

IMG_1281p.jpg

IMG_1282p.jpg

IMG_1283p.jpg

Show us a good schematic of the circuit.

.

Images from Reply #12 so we don’t have to download them. See this Image Guide

e9626dfb19955e18cfe27f6a2c6c9081c137e9fc.jpg

777e3e7e4b85f33d5badc18594ef67d96897ff67.jpg

d2238b3115b0c15d270d9ddb6d11da23a8785f44.jpg

43d51d2f19174f8bd8a83c5d2ab1fb9a355e9d0b.jpg

…R

Images like that are no assistance unless one wants to count capacitors. Post a schematic as requested by @larryd

...R

Ok, so I borrowed a tabletop power supply and found that the problem is the power supply to the servos. The servos are pulling about 5.5 volt and .5 amps at rest. Does anyone have a recommendation for the best battery to use for this?

Thanks

What is a table-top power supply - unfortunately the live cam from your kitchen is not working.

How many volts and amps can that power supply provide?

And post the schematic for your servo board!

…R

Robin2: What is a table-top power supply - unfortunately the live cam from your kitchen is not working.

How many volts and amps can that power supply provide?

And post the schematic for your servo board!

...R

Sorry, as I've mentioned I'm still new to electronics. So I don't know the names for things or what information is important.

The power supply is like this one.

I have no idea how much power it can provide, but why would the amount it can supply matter when it told me how much the servos draw when all are on 5.5 volts and.5 amps.

I haven't uploaded a schematic because I don't have one and didn't have time to make one last night. Why do you need a schematic though when the problem has been narrowed down to the power supply?

Sprint44:
I have no idea how much power it can provide,

I would be amazed if that information is not in the datasheet that you have not provided a link to.

but why would the amount it can supply matter when it told me how much the servos draw when all are on 5.5 volts and.5 amps.

Almost certainly it is measuring the average current rather than the peak current that might be required in an occasional millisecond when the motor accelerates.

…R