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DeveloperPermalink Reply by R_Lefebvre on December 12, 2011 at 9:46am

Yeah, I cut out a corner as well to fit the silver box.  But then I tried to figure out how to route the capacitor and filter and wires.  I didn't want it on the "bottom" near the microphone, because I needed to fit the heater resistors and foam on that side.  So they had to go on the backside.  I soldered the cap and resistor on, and glued them to the board.  Now I had no flat surface to mount on, and couldn't use the moon gel pad I had cut to fit.  Ok, I'll make some stand-off spacers.  But one of the holes is way too close to the pins, so I couldn't make a spacer out of the 3/16" aluminum rod I had.  I ended up just using rubber servo dampers as spacers.

 

I also used shielded wire. I think my sonar is done now.  Just have to run the wires to the GPS and Mag which are on the T-tail, finish rebuilding the head, and I'm good to go.

 

I got sidetracked a bit with my camera mount project as well.

 

As for the regulator, I am happy with it, but always open to constructive criticism if I've made a mistake.

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DeveloperPermalink Reply by R_Lefebvre on December 12, 2011 at 7:04am

No, I didn't but I will.  Thanks.  I looked at those sheets but it's all mostly greek to me.  Does it matter if I use bigger capacitors?  I don't have any that small.  It says 0.33uF and 0.2uF, but I've got... well in the 100's of uF anyway.  In fact, I was using my 16,500uF capacitor bank after the circuit, so it is essentially between Vo and ground.  Just need something on the input side.

 

 

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Permalink Reply by Ruud de Rooy on December 14, 2011 at 11:46am

Yes the 0.33uF is for making it stable if you put a big capacitor there i won't have the same effect.

on the supply side so the 5V little bigger is no problem.

 

But have you put the 16,500uF directly on the 5v of the l7805?

Because that could lead to high current draw at beginning of power-up could damage the l7805 you will exceed the 1amp.

better to stick with lower capacitor think that i would not go over the 500uF or make a current limiter with your L7805.

 

Ruud

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DeveloperPermalink Reply by R_Lefebvre on December 15, 2011 at 12:29pm

Hmmm, I replied to this yesterday...  but it's gone.

 

Ok, so what I discovered yesterday and today is that yes, you're exactly right.  The L7805 needs those small capacitors connected to it, because the small capacitors have less inductance than large ones, therefore they can work to smooth out fluctuations at a frequency higher than a large cap can. 

 

However, the small ones can be used in combination with the big ones.  This is commonly done.  Large caps to filter noise from an AC-DC power supply, and then small caps to filter RF noise. 

 

I picked up a .33uF and .1uF ceramic cap which I'll solder onto the L7805 pins directly.

 

It doesn't seem like the L7805 has a problem charging the cap bank.  If I've done the math right, the cap bank will only draw 1A for 0.0825 seconds to charge to 5V.  I know that when it starts charging is acts like a dead-short for a period of time.  I'm not sure if this can damage the regulator?  Certainly it's not a problem from a thermal standpoint.  And there is built in resistance in the chip that might limit it naturally.  Is it a problem for the amplifier?

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Permalink Reply by Ruud de Rooy on December 15, 2011 at 2:48pm

Yes you can combine small and large caps.

And you are probably right about the cap bank too the high current will only be a verry short peak.

still haven't had time to install my on board but i will probably make similar modifacations to my board.

will prob be next year before i have time :-( (promised my wife to paint the house so have to paint during the holidays)

 

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DeveloperPermalink Reply by R_Lefebvre on December 19, 2011 at 10:14am

Yesterday I added the small caps to the L7805.  I ran shielded wire for the GPS and Mag on the tail.  I believe my APM installation is finally complete.  Now I just need to fix the mechanicals.  I was hoping to fly yesterday, but it just didn't happen.  Winter is here, and I promised my wife I'd paint my daughters room in the winter... she's holding me to it. :(   ;)

 

Might after to wait until the week after Christmas now.

 

 

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DeveloperPermalink Reply by Randy on December 20, 2011 at 4:01am

Robert,

     What are you using for the shielded wire?  I'm still getting some sonar noise on my heli...I'll probably just wrap a ground wire around the whole thing but wanted to know what you were doing.

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DeveloperPermalink Reply by R_Lefebvre on December 20, 2011 at 5:15am

Something I grabbed at work.  I work in a wire factory. ;)  I've got some 3, 4, and 6 conductor plus drain, shielded wire cable.  I think 18ga IIRC.

I've actually thought about looking into a special run of product just for us, if there was any demand.  What I'm using is a bit big and stiff.  It's just ok on my 600, but might be a bit silly on your 450.  But I'm not sure if we're really set up to make what we need.  We do more industrial stuff.  I think what we need is like a 22ga, high strand count, high twist.  All for flexibility.

I've also cut the cords off some mice and things like before throwing them out.  But that stuff is a bit too small.  28ga.  It's hard to work with.

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DeveloperPermalink Reply by Randy on December 20, 2011 at 5:37am

    thanks for that. 

     There probably is demand for it as I've heard it discussed before as something that should potentially be supplied as an option with the sonar.  A decent number of people have trouble with this.  I think you're right about flexibility being important...and also not too fat/heavy.  ok, i've got an old mouse that may be sacrificed.  If i search the web I'll look for something 22ga or higher.

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DeveloperPermalink Reply by R_Lefebvre on December 20, 2011 at 7:16am

Yeah, I've actually thought about producing something that DIYD store would sell.  Maybe I'll look into it a bit more.

 

28ga would be fine, it's nice and small and flexible, but it's hard for human hands to terminate.  22ga is typical for servo wire, and it's just nice.  One of the issues trying to do something here is that I think we just don't do anything with that fine of a strand, and we don't have jacket material that is flexible enough.

 

I wonder if a braid would be better than foil shield in any case.  That would actually be easier for me to do in a small batch.

 

Ultimately, somebody probably already makes exactly what we need, and it would be just easier to buy it.

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DeveloperPermalink Reply by Randy on December 20, 2011 at 5:52am

I improved the sonar scaling over the weekend so you will see it better in the next release.  In fact it's already out in the 2.1 quad code.  This will likely fix the 85cm vs 65cm but you'll find the sonar never reads less than 20 or 30cm..this is a limitation of the sonar..it can't send the noise and then be ready to hear the reply in less time than it takes the sound to travel 20cm.  This is a built in limitation of the sonars which use the same 'speaker' like thing for both sending and receiving the signal.

 

the noise i was talking about was little spikes that appear in the sonar measurements, often caused by interference from other sensors, escs, etc near by.

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DeveloperPermalink Reply by Randy on December 20, 2011 at 7:22am

yes, there's some short advice on the wiki page at the bottom and there were some discussions in the forums as well like this one.

 

basically it depends on the source..it could come from the power supplied to the sonar in which case you need some caps added.  or it could be from nearby sensors (which you've likely resolved) or it could be caused by interference on the cables (in which case you need a shielded cable)...so many possibilities!

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