C200H-NC213

[LSV 0]

I have to monitor rpm of my servo on HMI. Do not know how to convert pps from DM508 to rpm using CX-programmer (for ex.: I have 5000 (in hex) in DM508, what speed in rpm does it correspond?) Is any special coversion instruction or formula? I'm using C200HG, NC213, servodrive R88D-UP12LA, and AC servomotor R88M-20030LA. Thanks. Edited 7 Apr 2005 by LSV

[Sleepy Wombat 27]

Not sure of the servo you are using, but heres a guess.... How many pulses does it take to do one revolution ???? For example if it required 500 pulses for one revoltion then Divide the pps (pulses per second) by 500 and that should give the Revolutions per second of the motor. In this case it will be 5000 / 500 = 10 rev per sec. To convert this to RPM multiply the result by 60 (ie 60 seconds in a minute) therefore 10 * 60 = 600 rpm...

[LSV 0]

That is exactly what I did. My motor needs 20480 pulses for one revolution. When I set speed to 341pps (20480/60), it makes 1 rpm. When I doubled speed (682pps), it makes 2rpm, but it works till 9rpm (341*9=3069pps). Then this formula does not work. If I write to DM508 5000pps, it makes 30rpm. When I write 6500pps, it makes about 75-80rpm (I counted when watching the motor). It some how relates to hex system, but I can not get how. Thanks for reply.

[mlarkinp 0]

It sounds like you are mixing your bases. Are you sure that all the numbers you are using in the calculation are in either Hex or Decimal? They all have to be in one or the other for the formula to work.

[Nibroc 4]

Hi, Also check that you are using double word maths. The C200H NC unit operates with BCD numbers? You should then use ADDL(054), MULL(056), DIVL(057) etc. These functions work with double word BCD values. You will find that the numbers and calculations you are dealing with cannot be represented with single words. Nibroc

[LSV 0]

Hi, thanks everybody for reply. Yes, C200-NC uses BCD, and it is good you pointed that I have to use doubl word math. I'll try to do conversion in ladder later. At this point I can't figure out using just a calculator. It seems to me the output (motor speed in rpm) is not linear after 9 rpm. Otherwise do not understand why 341pps(hex) gives me 1rpm, 2728pps(hex) gives 8rpm, and 5000pps(hex) gives 30rpm, 6500pps(hex) gives about 80rpm. I got these numbers by experiment. Did some body have this kind of problem or it because I do something wrong?

[Nibroc 4]

Hi again The R88M-20030LA Servo Motor has a 2048 pulse A,B + Z type incremental encoder. This motor with the electronic gear ratio (set in servo driver) set to 1:1 would require 8192 pulses per revolution (because of quadrature A/B pulses of encoder). With the electronic gear ratio set to 4:1 it would require 2048 pulses per revolution. I assume your G1/G2 is set to 5/2 (5=G1, 2=G2) thus giving a 2.5:1 ratio and giving 20480 pulses per rev. Thus if you set 20480/60 = 341 (approx) pps for 1 rpm (as you suggest) Be careful with your calculations, in BCD 6500 = 6500 decimal, in Hex 6500 = 25856 !! 6500 / 20480 * 60 = 19 RPM 25856 / 20480 * 60 = 75 RPM!! BCD 5000 = 5000 dec, 5000 Hex = 20480!! 5000 / 20480 * 60 = 15 RPM 20480 / 20480 * 60 = 60 RPM!! BCD 2728 = 2728 dec, 2728 Hex = 10024 2728 /20480 * 60 = 8 RPM 10024 / 20480 * 60 = 29RPM!! For BCD calculation do all your manual calculations in decimal, (simply read hex values as they appear DO NOT CONVERT THE HEX TO DECIMAL). Note also: CX-Programmer may display a BCD value with a HEX suffix (depends on the symbol setup/display mode) - never fear HEX values are BCD if you read them that way!! Not also that C200 NC has a speed unit multiplier system, you can multiply your pps setting by 1, 10 or 100. eg speed #3413 BCD x 10 = 34130pps = 100 RPM approx (for your application) Note also that max motor RPM with your configuration (G1/G2 = 2.5) is: 200000 (max C200 NC pps) x 2.5/8192 = 3662 RPM Nibroc Edited 10 Apr 2005 by Nibroc

[LSV 0]

Hi, I just had a chance to check the replies. Thanks very much for clear and usefull explanations. I will play with numbers.