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Asked — Edited

Separate Power For Hd Servos

I have several HD servos to operate so I need external power supply. As I am inpatient to wait for ez bits, how do I go about supplying external power for these servos? I am okay with modifying the EZ-B v.3, I just don't know what I need to do. Help, anyone?

I have them attached in the smaller block of DIOs and was wondering if it was possible to only alter these, or if the alteration affected all DIOs?


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@bret.tallent so no ground from the separate 6volt supply to the board?

Like this then?
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That is how mine is set up and it works great.
Yea rich that's the best route to go with , seperate power supplies , I recommend not using the AA battery holder , either use a 6v lead acid or just another battery of choice your using on the servos, dj said he managed to get a all day run time using ub645 6v 4.5ah battery that usually go in a omnibot
Thanks guys,

I will be using a 11.1volt 3500mAh lipo for the lot with a 8amp UBEC at 6volts for the servos. I can plug the lipo (will have a lipo alarm) straight into the EZ-B though, is that correct?

He will also have a small 6volt Nimh pack to drive his charge level panel that will be able to be solar charged when he opens his solar panels.

Wall-e will be having 17 or 18 servos plus a heap of peripherals this would mean that I will need two EZ-B boards from what I have read and been told.

I will try and get some progress photos done tomorrow.

Maybe you could use a portable 12v 3s Lipo charger in the bot , wire up your panels to produce close to 12v and you could have onboard charging. There are marine and auto 12v solar panel sets for 30 to 40 dollars you can use as a donor.
It's funny I was working on a post that incorporated RichiesRC's first daigram which is correct, the second one is incorrect. The reason being is that the signal going to the servo has to have the same ground reference as the external battery supplied to it. The easiest thing to do is to connect both negative battery terminals together (just be careful not to mix up, or connect together, the positive terminals of the batteries). In RichiesRC's first diagram he had the negative post from the 6V battery going to the GND rail on the EZ-B which is totally OK.

It also hasn't been mentioned that the EXT PWR SEL (External Power Select) can be used in this case for D0-D14 pins, you just cut the trace underneath the board and solder your 6V from the battery to the solder pad closest to the D0 pin. This way you don't have to put any external wires to the servo, just plug it right into the board as you usually do. This idea was brought forward from the original EZ-B boards which all had an external way to supply power to your servos if you wanted to use large torque servos.

I guess a discussion that has already been started is one about battery selection which is also very important in high torque motor use. I suggest we start a new thread about battery selection.
@skater , if they go back to the same battery then there is a common ground , they are just avoiding routing it through ezb due to current restriction
I was wondering because the electric car I'm building has the drive system isolated from the car systems even the ground is isolated
skater_j10 is right on, first diagram is correct. Diagram 2 may work but you could also have some strange things going on if you don't provide a reference ground for the signal, especially if you run that wire by motors or where emf could be induced on it.



Thanks for the info, I now understand it much better and thought it was strange that my first diagram was wrong as I tried both methods using a RC receiver and two separate power supplies, a 4.8v to power the receiver and a 6v to power the servo and my second diagram did not work. The diagrams were for reference only and as I am a electronics dummy. As I will be using a common power supply and the ground will be common.
Also if you have the or know where I can find the "how to" on the EXT PWR SEL would be great, I have no problems if I have clear wiring diagrams and instructions and my soldering skills are good.

Good idea that someone starts a new thread about battery selection.


Great idea and I have a spare lipo charger(12volts/5amp input)but Wall-e is not that big and his solar panels(60mm x 60mm) only put out about 3.5-4 volts each not sure what amperage but those chargers need a constant 5 amps. I could add 2 more panels but where do I stop..lol this project will never get finished.

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Hi rich , only go for the sorta flat black solar cells , they produce more current. If you use these they are :30ma per 12v paralleled set. So 60ma is feasable , you could only charge a nicad or lead acid with a slow charge though. Here's a tiny suggestion , cover your whole bot in them , leave the ones ontology of walle eyes/head uncovered and maybe ones on his back. When you go to paint cut it down with clear so the paints translucent , it reduces the efficiency of the solar cells but you can make your walle yellow and charge all the time. Second concept is having two small batt , and a switch. So one battery is always slowly charging from ambient light. If you have his normal array Plus hide some cells under paint you.May get 1-2 amp is direct sunlight to charge him.
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Cover up flat spaces with these , walle is a box so this is easy. Cells can be cut as long as you don't cut the main connection , cutting them reduces voltage to plan to connect cells for 16 to 17 volts so after losses you still have 13-14v for charging
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Part No. : D5733 . Voltage : 6 Volt . Capacity : 4.5 Ah . Chemistry : Sealed Lead Acid . Color : Black . Height : 4.17 in. . Width : 1.85 in. . Length : 2.76 in. . Start Temp. (Min) : 5 Deg. F . Start Temp. (Max) : 104 Deg. . Terminal : F1 . Weight : 1.83 lb. . UL Listed : Yes .Warranty : 1 Year .Order Code : UB645

Just bought two for 18 USD shipped New!


These will accept a low ampere charge well , sealed , gel/glass filled
Thats the thing about those is easier charging .
That's what I'm using on Omnibot, BOB. I have one in him and it works fantastic! I power the board, and also my motors and HD servos off this one battery. That way everything shares a common ground. Speaking of charging, what would I need to charge one of these batteries (haven't needed it yet)?
AGM and gels last a lot longer if you slow charge them. Keeps from drying them out. I'm not sure about the voltage on a 6 v but 12v ones are 14.1. I would guess half at 7 volts and 6.2 to maintain
A slow charge is 1.7 -2 volts over the battery rating at a rate between .7 and 1.5 ah . I bought a motorcycle computerized battery charger /maintainer that charges 1.5 amp from walmart. But I have 2 batteries so that's .75 ah per battery which is optimal slow charge. I leave them overnight. The charger I bought from walmart for 6 or 12v batteries was 20 bucks.