[ulihuber]

eternauta3k,

Sorry everything is in German

please tell me what you are missing. What documents are you referring to ?

I guess there is almost every bit available in english too. Even the commands were translated for the ease of usage for you US guys.

Please look at www.uhu-servo.de and click on the english flag. It's valid for US people too... ;-))

The only thing I can't change is the language in the german forum. If they wanted to speak english, they would have become members of CNCzone instead.

Uli

[eternauta3k]

Don't worry, I'm not missing anything. Just refuting the quote, your page's OK.

[ejkoeze]

Don't worry, I'm not missing anything. Just refuting the quote, your page's OK.

And the quote was from before I knew of the English version of the document.
There is no need to counter old statements that may have lost meaning or relevance.

Erik Jan

[jrz126]

I finally got my circuit board all soldered up...and it doesnt work. I'm having the same problem that I was having when I had it on my breadboard. The encoder only seems to be responding only in 1 direction. Also, the wrap count is counting up.
I'm going to get my oscilliscope on the encoder later this afternoon. (are the pull up resistors on the encoder output necessary?)
Also, do I have to send a command to the micro to tell it to hold the motor position? It doesnt seem to be attempting to drive the motor at all.

[slp_prlzys]

I made me a version of UHU servo
that uses LMD18200T, I got me 3 chip
from Uli (thanks Uli), and I happen to have 18200t.
the first version I have is the uhu555, I didn't use a Max232 chip,
as I already have Max232 board.
The setup works, well sort of, I may have goofed
on the value of my sense resistor, and the value of
my R20 and R19, and I'm using a 10k trimmer.
I used 4k7 on R20, 3k on R19, and my sense resistor
is 1k. LMD18200 specsheet says that for every Ampere
of current load there's 377uA on the sense,
I set it up so I could use 2Amps. Did I do it right?
I should get .754V at the sense R using 1k and 754uA,
I tried to setup the trimmer so I could get a .74V bet. R20 & R19,
I'm partial with it as I have cheap DMM, I don't
think I could get accurate measurement with less than
1V. It's working but as soon as the motor turns,
the current limiting LED blinks right away, I don't
think the motor is consuming more than 2Amps yet.
so there must be something wrong with the settings.
(but it's nice to see that part of the circuit works,
BTW I'm using tl072, got it from scrap board, 'been reading
'bout OpAmp, and found it really interesting).

My next version uses max232,
if someone could look into it, give some feedback?
so I could do it right this time. Note, that
I use a modified library of Eagle4.16 light so
I'd be able to solder most of the parts without
drilling sort of smd style (I do get layer abuse error tho.
can't blame the thing it's right )

Oh, I forgot the fun part, the 3rd time I test the uhu555,
I blew up the LMD18200T, I stupidly switch the pos/negative
on it's supply, now I know what the "magic smokes" meant.

(I don't think tuning servo is gonna be easy)

[zoltan]

Hi,

Could you, please, share with us your eagle files?

Thank you,

Zoltan

[slp_prlzys]

I don't think you'd be able to see the board
laid out as mine as I have modified the library,
I'm gonna need to search for it, if you need it.
Note: all DIP ic are on the copperside, I'll
be using sockets for them, with pins bent outward.

[vroemm]

Hi..

The UHU Wiki is starting to get shape and content.
What do you think of it so far ?
http://gsst.wikispaces.com/

[zoltan]

Thank you for files. They work.

[dfv]

Zoltan did you make the design of slp_prlzys with the lmd18200t? does it work?

[zoltan]

Hi,

Sorry for misunderstanding. I was reffering to: "I don't think you'd be able to see the board laid out as mine as I have modified the library,..." so, I could see it, and I have just made the pcb to give it a try.

Zoltan

[zoltan]

Could someone suggest some DC servos for this controller, including encoders, that I can buy from European supplier as the shipping fees are too high for buying from US.

Thank you,

Zoltan

[ejkoeze]

If you can read German you can try www.ebay.de They usually have a shipload of suitable dc motors. Keep the selection criteria in mind.
Encodercount between 250 and 500 CPR, low rpm (below 3000 RPM is best) low no load current (way under 1A).

Erik Jan

[max_imum2000]

ok a lot of contradictions and questions i cant see it clear!!

why cant we use STP40N20 power mosfet instead of the 260s ? it is much cheaper and almost have the same ratings ?


a lot of people here including uli says that we can use diodes like 1n4001 and other says no dont use it ? so can we use it or not (instead of all the diodes)

in motor suggestions you say "no load current below 1amp" ?, why
isnt the driver suppose to handle a lot more than that ? shouldnt we be looking at permenant current of the motor at the rated speed ?, and for the peak current at stall, instead ?

in some part list it shows standard capacitors , should we really use MKT and Tantalium ones and so on, or really the standard electro and ceramic will do the job ?

thank you all for great work

[ulihuber]

Max~,
when I said

Should all be MUR120 or HER105 ?
just replace them all by the type which is best available.
The diodes are not critical, not in voltage nor in current.

I thought to replace the two types with any fast switching type. Standard 4007 could work but why taking a risk if you cannot save more than a few cents ?

Concerning the FETS I can tell you that ANY Power MOS Fet I tried in the past worked more or less. As well as IGBTs. The difference is power dissipation because of high Ron or slow switching characteristics. International Rectifiers call their IRF 'the best power MOS-Fets of the world' . We thought this should be the minimum for our project... ;-))).
The hard restriction to IRF540N was necessary for the old board with IR2104 drivers. They could not charge high gate capcities.
Give your FETs a try !

The motor question is a bit more complicated because of all you guys who want to employ every part that looks like a DC motor. But it makes no sense to build a servo controller and to use a scrap motor which is not able to move smoothly.
A good DC motor starts mit minimal voltage and runs without pulling a lot of current if there is no load applied. For example I have nice 20 pound DC motors that start moving with 1 (!) AA cell. 1.5V and less than 500 mA.
Having more than 2 brushes is not a must but experience shows that those are the better ones.
Another subject is heating up. Cheap motors very often are not able to deal with the power dissipation you have while turning at low speed and high torque.
Having more than 1A at no torque is not more than a sign for a motor which seams not to fit in the upper description.

To sum up: Invest whatever you saved with the FETs in the Motors.

Most capacitors are all not critical. Use MKT types or ceramics whatever you get for the blocking Cs. Those few 1uF around the MAX232 should be Tantalium. Or you switch to MAX202 and use 100nF ceramic instead.
Don't try to save money at the power capacitors. Buy those with 85°C or 105°C and low ESR. It's no fun having one of them explode in your casing.

Uli

[max_imum2000]

some of us just live in remote places where finding parts are not that easy and have to work with what we have (ex: the diode types)
ordering the part from the us or europe will cost about 5x the value when calculationg shipping and so on

so are the max202 pin to pin compatible ?

thanks uli for all your time and help, what can i send you from Egypt ?

[ulihuber]

Max~,

its not the cost its the avilabilty

thats definitely something I understand. Do you get IR2184's ?

MAX202 are pin compatible. I always have those on my own boards.

While I am unable to prepare kits for all interrested people I might help in certain cases with some parts. Send me an email....

Uli

[slp_prlzys]

Zoltan:

I am waiting for feedback on that schematic before
I actually build it. I made a mistake on the schematic. D4
is meant to be placed on the motor supply side, I used
it sort of polarity protection, but I didn't realized I had
it in the logic supply side. Anyway you could always use it,
or just have it jumpered.

let us know if it works.

[smarbaga]

Hello All

In reguards to the promised uHu Servo Controller Kits.

I have today recieved the atmel uHu Chips, from Uli.
The PC boards were shipped from Canada today.
I now have all the electronic parts.

When the pc boards arive (which should be 4 days ) i will assemble one and make sure everything functions as expected.

Kits or Assembled and tested units should be available in 10 days from today.

Sorry about the delay. The first batch is always the hardest, I guess.
thank you.

[Syp]

Hi,

I was looking over this very impressive servo controller board (very cool that a group like this exists!) and had a question about the schematic.

What is the purpose of the power mosfet gate drive components, like C36, R9, D1, and R1. These are used to drive the gate of each mosfet. To me it looks like when the IR2184 half bridge driver chip goes from low to high, the power mosfet gate charges through the 22R value resistor and the capacitor, with the 270R resistor present for the steady state condition to keep the gate fully on. When the half bridge driver goes from high to low, the power mosfet gate discharges through the 22R value resistor and the diode (and the capacitor).

Why have all of that instead of one single gate drive resistor???

Thanks!

Syp