Encoder to Resolver converter?


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Thread: Encoder to Resolver converter?

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    Default Encoder to Resolver converter?

    Does such a thing exist?

    I have a Baldor servo drive that is set up for using with a resolver. I also have a spare servomotor with a quadrature encoder.

    Is there any way to use these two together?

    Baldor consider it not economic to fit an encoder board and reconfigure the drive (Mint MDH2A.,.,) so I wondered whether a converter exists. There are lots of resolver to encoders but they are the wrong way.

    Ian P

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    Member mike_Kilroy's Avatar
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    they are the 'wrong' way for a reason; it is simple to use a cheap IC chip and convert resolver to encoder sigs. going the other way has 2 major problems that prevent most people from making such a gidget:

    1) encoder pulses only change sometimes, so between changing, there is no information to help make a nice sine wave so the resulting sine wave has lots of steps which make controlling servos hard.

    2) most of time today when a cheap incremental encoder is in a motor, there is also ANOTHER device to give absolute information (typically halls or hall type (commutation) channels). Without this info, the resolver cannot be absolute so the motor cannot be made to commutate correctly. There are ways around this but they are either nasty or add more expense to the converter gidget making it not worth making.

    Maybe someone has a Mint thing w/encoder feedback you can buy? ebay? list full part no and we can check the dusty area of the warehouse - I think we have a box with 3-4 Mint things in it... maybe others do to?

    that said, if you want to investigate it anyway, one of the products we sell is this, called SC100 & SC200. check it out here: www.newall.com

    Mike@@@KilroyWasHere.com


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    Mike

    Ah! now I understand why nobody makes suitable converters.

    The drive I have is a MintDrive MDH2A02TB-RC20 if that means anything to you. Its single phase input and outputs are rated 2.5A.

    Not having a suitable motor I have not been able to use it. Baldor would convert it to encoder input but if you dont come across anything in your dusty storeroom, I think I will sell it and get something else.

    Ian P



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    Default Re: Encoder to Resolver converter?

    Quote Originally Posted by elanman99 View Post
    Mike

    Ah! now I understand why nobody makes suitable converters.

    The drive I have is a MintDrive MDH2A02TB-RC20 if that means anything to you. Its single phase input and outputs are rated 2.5A.

    Not having a suitable motor I have not been able to use it. Baldor would convert it to encoder input but if you dont come across anything in your dusty storeroom, I think I will sell it and get something else.

    Ian P
    Time to revisit this! We have some projects where we need square wave TTL encoder sigs converted to resolver sin/cos signals. So we have designed a basic unit block diagram how to do it; not too difficult. Here is an RFQ I am sending around looking for someone to build this if it still does not exist:

    We have a project where we would like to design a simple FPGA based signal converter. Our use would be to change an encoder signal into a resolver signal; what that means is a string of 5V TTL input pulses come into our converter and come out as a 20Vpp sine wave. Each converter needs 2 channels, a sine and a cosine (90 ele degrees offset from the sine channel. Our source will give us both of these TTL pulse strings.

    We want to make a sine wave from 16 bits of input; ie., 65,535 increments in will make one complete sine wave output. Then it repeats. So if we send 65,535 pulses per second, the output of out converter will be a 20Vpp 1hz signal. Max input freq of pulses will be 200 Khz.

    The sin & cos inputs are available as differential 5V signals each, and we will want differential 20Vpp sine & cos outputs.

    If we can make this easy and low cost enough, each application will require 6 pieces. We project 3-4 applications per year for 5 years, so about 120 total of these converters.

    Is this something your group would be interested in designing for us?

    Anyone interested in building this??



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    Default Re: Encoder to Resolver converter?

    Heidenhain make/sell sine wave convertors for their common sine output types, but the problem with converting a resolver to quadrature square wave is although quite simple to do, the down side is the resolver is generally a low res output when used this way.
    They are intended to be used with sine-cosine co-tangent calculator for hi-res.
    Do you just need sine-cosine 5v to 20vpp convertor?
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: Encoder to Resolver converter?

    ya but I want the OTHER way... heid always had their EXE boxes to go frm sine to TTL. I need to go from TTL to sine... at 16bit resolution... easy to do with an FPGA look up table but no one makes one. Guess not enough market for it.



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    Default Re: Encoder to Resolver converter?

    So you just need a 5v square wave to 22vpp sine?
    I could look into a design if needed.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: Encoder to Resolver converter?

    Quote Originally Posted by Al_The_Man View Post
    So you just need a 5v square wave to 22vpp sine?
    I could look into a design if needed.
    Al.
    Yep & SWEET! If this is something you would do, I'd love to buy it from you instead of someone else!! See my post #4 for most details I think needed to design it. We would buy the design or full pcb's or whatever.

    I even researched a bit what the FPGA lookup would look like; found cool description (attached)

    Attached Thumbnails Attached Thumbnails Encoder to Resolver converter?-generatingsinwlookuptable-pdf  


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    Default Re: Encoder to Resolver converter?



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    Default Re: Encoder to Resolver converter?

    I use the Picmicro products, but would look into a non-processor based answer first, can't promise anything, also depends on time constraints.
    Is there size constraints? I usually get boards made up from Hong Kong.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: Encoder to Resolver converter?

    Quote Originally Posted by Al_The_Man View Post
    I use the Picmicro products, but would look into a non-processor based answer first, can't promise anything, also depends on time constraints.
    Is there size constraints? I usually get boards made up from Hong Kong.
    Al.
    OK to keep tweeking specs and discuss this here or should we go offline?

    We may have to change input to 0-10vdc 16 bit position word or some bus like ethercat, profinet, etc - we may need to know the position on power up and TTL incremental won't give us that.... the position is coming originally from a 2 pole resolver feeding a servo drive. we can get TTL encoder emulation, communications bus, or 0-10vdc output from this resolver to 'make' our new resolver signal... reason we need this black box is we need to have a variable multiplier from .01 to 100 times the original resolver. this is a device to replace mechanical PAU with gearing between the moor and this second resolver. The servodrive does almost infinite multiplication on the original resolver so we do not have to worry about that part of it. Just reconstruct a resolver signal for a CNC control with a variable gear ratio. typical ratios are .5 to 3:1 in reality.



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    Default Re: Encoder to Resolver converter?

    a variable multiplier from .01 to 100 times the original resolver.
    or even just typical ratios are .5 to 3:1 in reality
    Through a digital channel?
    Alarm bells start to ring.
    An uneducated guess would be asking whether you are trying to get more resolution out of a digital signal than you are putting in?
    I suspect you will need to stay entirely in the analog world for this, OR go to very high ADC/DAC resolutions - extremely high, and quite expensive.

    Cheers
    Roger



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    Default Re: Encoder to Resolver converter?

    Quote Originally Posted by RCaffin View Post
    a variable multiplier from .01 to 100 times the original resolver.
    or even just typical ratios are .5 to 3:1 in reality
    Through a digital channel?
    Alarm bells start to ring.
    An uneducated guess would be asking whether you are trying to get more resolution out of a digital signal than you are putting in?
    I suspect you will need to stay entirely in the analog world for this, OR go to very high ADC/DAC resolutions - extremely high, and quite expensive.

    Cheers
    Roger
    Thanks for thoughts Roger. Just to clarify, there is no attempt here to make more resolution from less. We already have a drive that does the magic of changing a 31 or 32 bit per rev position word into ANY scaling we want, and it outputs ANY TTL enc equiv count from 1 to about 65,000,0000. So it does the scaling for us.

    Our need is to grab this scaled position in one form or another and turn it into a sine/cos with 15 bit resolution. It is the scaling we need to do, and that is done for us for free already. All we need to do it convert this scaled position into a sine/cos format. We initially thought using the free incremental quad encoder emulator output would be best as it can simply increment thru an FPGA lookup table, but issue is the dual X, X' axes on these gantry machines look at the position feedback ON POWER UP and automatically adjust any skew out; So although the incremental encoder sig works fine AFTER THIS, we loose this important feature. So we need to start with a position word that on power up has absolute data, thus change to input for our black box needs to a profinet,, ethernet, ethercat, etc, or assign the free 16 bit analog output to be position and use it.

    In all these cases we do not need to do ANY scaling, multiplying, dividing to get that .5 to 3x range as it is done for us in the drive already.

    To be clear WHY, these fantastic CNC older controls require resolver feedback, and that feedback MUST be 1 sine/cos cycle output = 0.200" It is a 16 bit input, so any more is wasted, any less will cause issues = .200". So to make ALL axes on these machines give 1 resolver rev = 0.200" requires GEARED resolvers. We believe with our great free scaling in the new drives we should be able to build a black box to do the same.



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    Default Re: Encoder to Resolver converter?

    Can the drive simulate an absolute encoder? Say SSI or BISS?
    These would make conversion simpler since the FPGA/uProc
    would not need any complex protocol logic



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    Default Re: Encoder to Resolver converter?

    Quote Originally Posted by PCW_MESA View Post
    Can the drive simulate an absolute encoder? Say SSI or BISS?
    These would make conversion simpler since the FPGA/uProc
    would not need any complex protocol logic
    dang! wrong drive... we have SSI output on another series but not on the AKD yet... We can output SSI so have the 16bit 'absolute' position word we need. I just saw a FPGA set of boards by a company with a similar name to yours, Mesanet.com, and sent them an email... I neglected to include SSI as available to work with; thanks for the miss - I will resend that to them also.

    I need to check availability of SSI output - not there.



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    Default Re: Encoder to Resolver converter?

    We have the drive mfgr thinking about adding the SSI protocol, but it is not there today... I am leaning more and more towards taking the absolute position data from the 250usec update rate of EtherCat bus as input... Wonder if the Mesa card folks have messed with it yet?



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Encoder to Resolver converter?

Encoder to Resolver converter?