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Asked — Edited

Supercaps On 3.3V Rail, Preventing Ezb To Connect?

@Jeremie I hate to bring this topic up again, ( its been about a year ) :)

Back last year I put two SuperCap rated 1.5f @ 5v in series ( 1.5f 10v ) on EZB's input servo power ( 6v Battery ) to prevent brownouts and its been very successful, and worked well. ( Stopped brownouts ).

But since converting some of InMoov's large scale HS-805BB servo's over to EZ-Robots HDD Servo's I've been getting Brownouts? So I tried various things but still kept getting brownouts.

I then put one of the 1.5f 5v caps on the 3.3v rail of the EZB as you recommended last year, but for some reason it prevents me from connecting to the ARC in Client mode? I've checked and double check and its wired up correctly and as soon as I've removed it, it connects OK! I've carried this out a number of times powering off and back on in-between and get the same results. I also tried other supercaps, just in-case these two have gone faulty, but still get the same result, regarding the wifi connection.

I measured the 3.3v rail, when the supercap is connected and its still 3.3v, so its not being pulled down at all?

Any ideas?

Cheers Chris.


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If you have to hack the ezb for your project, then you're exceeding the current limitations. Exceeding power limitations is dangerous and could cause risk of fire or damage out the ezb.

Power the servos from the power source directly using modified peripheral cables or something like the inmoov servo breakout board.

The ezrobot servos will logically use more current than a larger servo. This is simply because the gear ratios are less than half that of a larger servo. Simple math means the servo motor has to work nearly twice as hard. Thus, drawing more current.


@cem... For my first inMoov I pretty much and stupidly powered the entire inMoov through an ezb and an ssc-32... Later I used a "servo power" board to power my servos separately... I either use 2 x 6V SLA bats in parallel or a 6V 50amp power supply now... I do not experience any brown outs... You could also do is use a separate power source for you ezb ... This way the servo movements won't affect the voltage levels to the ezb...

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Yes, I should of done this in the beginning but was to eager to get started and finish, which is a bit of a joke, as it took me nearly a year to complete in the end, but to be fair to me I was diagnosed with a terminal illness in-between! As you suggested I should done this from the start.

But I still don't understand why putting a super cap on the 3.3v rail, stopped the wifi connecting? I know other have done this including yourself and haven't had this problem, hence why I've gone over and over it again to check I having made any mistakes or done something stupid.

@JD I do understand what you are saying and wasn't criticizing the HDD servo in any way, it a GREAT servo! I'm more interested in the above about stopping connecting to wifi in client mode with the cap on the 3.3v rail.

Thanks Chris.


Sorry to hear that mate. Dont give up... All the best.

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I had blader cancer stage 3. Did quimo and removed blader. That was 2 years ago. Doc says its gone. God i hope so! Regards.


Sorry for being off topic...


@Cem, darn it, that sucks totally. I'm sending strength and prayers your way. I'm sure the grace of whatever Higher Power or God you believe in will be by your side and help you and your family through these times.

As far as your power issue. I have to validate what others have said. Power the servos direct from your power source. You will never have a power issue again.

I wish I knew why the addition of the caps are keeping your wifi from working. Only a EZ Robot expert would know. I could speculate but it would only be a guess (power surge when the Wifi tries to operate?).



I did some tests today with my 2 x 1F 2.7V caps in series (0.5F 5.4V) on the 3.3V line, a EZ-Bv4.1/2, and 20 x HDD servos. I didn't have any trouble connecting in client mode. What does your setup consist of?

One thing to note is that once power is removed or reset you have to wait a full 15 seconds (probably longer for you since you have a bigger cap) for the Super cap to completely drain before powering back on, otherwise the chips get stuck into a weird low power state and you won't be able to connect. You can instantly recognize if the chips are in this state if you don't hear any audio on boot-up.

P.S. I'm so sorry to hear about your terminal illness. We are very glad to have you here. Thanks for your contributions to this forum!

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Thanks for testing it out, much appreciated.

It works with my IOTiny and another EZB/2. I've disconnected everything on the EZB and it will not initialize with the cap on the 3.3 rail. Take it off and it's works fine, bizarre!

Anyway I'm thinking of re-doing the whole power for my Inmoov, and have a separate supply for the EZB's, as Richard had suggested.

Building the InMoov and having EZ-Robots has been extremely beneficial regarding my illness, Its really been a real life line and kept my mind busy!

Thanks again Chris.


Hi Chris,

I just wanted to quickly clarify with you. This is with a EZ-Bv4.1/1? The older EZ-B version? By "initialize" do you mean that the RGB LED on the WiFi board flashes green but doesn't do anything, stays solid green on boot, or doesn't come on at all. Is there any Audio?

Did you have a chance to try powering down the EZ-B for, let's say, 30 seconds and then powering it back on?

I understand you are likely going to try a different power configuration but I'd love to figure out what's going on.



i had hodgekin canser.still get chemo x6.canser was gone allreddy after 4 chemo's. when you take a petscan.the doc can say and see 100% sure its gone. he can show you on a pc that the cancer is gone.petscan takes 10 min time.

cem keep building your inmoove.you are great.

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Yes this is the older EZ-B version, with the upgraded comm's board, like the other one I have.

The WiFi board flashes green but doesn't do anything, and doesn't connect to ARC, take the cap off, power back on and it connects straightaway, I can repeat this over and over again, it's always the same. I've waited for over a min before powering on when I put the cap on, although it's pretty much discharged as I leave it on after powered down, and can see the light slowly fading and goes out.

I'm wondering as I'm using a 1.5f cap, that on power up the in-rush current created by the cap, causes the EZB to go into this state? May be on this particular EZB It's on the its limits? I need to do some more testing, with lower values caps and see. But I'm going away for 4 days tomorrow, so it will have to wait until I'm back.

Cheers Chris.

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thats sounds very serious.i get contrast too before the scan. i find you very brave.i have hodgekin cat 4 of 5.so i gess i was lucky. ive seen many whit canser growing old,it has many faces. 50% of tumors are good.


@CEM - do not create new threads for topics that you have already started. A new thread with a single message doesn't have any relationship to anyone else reading it. I have pasted your message here below...



Just thought I'll give you an update, to close out on this.

I spent some more time with the supercap issue, and it does look like it works with a small value cap, I used a 1f 5v cap, and it initializes OK, but not with the 1.5f. 5v cap. I completely removed everything off the EZB ( standalone ) and it still doesnt initialize with the 1.5f, but does with a 1f, as I said before my other EZB and the IOTiny works fine with the 1.5f.

( I know I said it does initialize but doesn't just connect to the ARC, I was wrong I had the sound disconnected ). blush

Interesting I did use another 1.5f and it made it worse and the EZB buzz like mad! I assume it puts the EZB into a locked state may be something to do with the 'in-rush' current of the high value cap, pulling down the 3.3v for a few ms?

Anyway I'm going to redo the power on my InMoov and have a separate supply for the EZBs, and have the large SLA battery just for the Servos.

Once again thank you for your support, I want to thank EZ-Robots for designing the HDD servos, I know you put a number of years work into them, but it sure paid off, as they are just FANTASTIC!

Cheers Chris.

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I created a new post, as I got a bit off topic about my condition and thought it wasn't appropriate!


Thanks for the update @cem

Good to know that 1.5F Super caps on the 3.3V pins can cause issues in some instances.