Hello CNC2;Originally Posted by cnc2
The UHU board has its own opto-isolation for Step and direction signals, you just need to route the corresponding pins from the LPT port to the UHU boards, for that you don't need an opto-isolated interface.
jcdammeyer is right, although opto-isolation is not really required what could be required is a buffered board, sometimes the B.O.Bs include both, and that is why some people buy opto-isolated B.O.B.s without needing that feature.
Not long ago I posted a buffered interface board schematic, although it was designed for split axes (dual motor per axis) you can modify it for only one motor per axis. Here it is: http://www.cnczone.com/forums/showthread.php?t=49838 You can use only the Master Interface side.
If I find some good tutorials on basic electronics I will post the links, just do a search, there are many available on the web.
Kreutz.
Thanks a lot Kreutz !
The UHU is already opto-isolated so it won't fry my motherboard, thanks, these are good news !
So, this 5 axis interface can do the job http://pminmo.com/PMinMOwiki/index.php5?title=5axis Am i wrong ?
The problem with electronics ain't in searching, but it is in "where to start from?" electronics are so vast, it's discouraging !
Thanks !
cnc2.
Hi rokag3,
No, this is my only working test board, I am building 4 more for the machine but they still need some more components to be fitted in order for them to work.
My only differences from the original schematic /that I think may be putting out my problems/ are that I have put BZW06-15B /which states for P6KE18CA/ instead of the P6KE12CA, and that I have used IRFP150N mosfets. Maybe Kreutz can say if the different transil diodes will behave badly in the schematic. The problem here in BG is that there is no place where I can buy the proper ones, or if I could order I have to buy some 100 items, for example. In fact these are the components that the other 4 board are waiting for.
Todor
.Maybe Kreutz can say if the different transil diodes will behave badly in the schematic
I am absolutely not the good guy to answear this problem
in greece we have the same probleme , i find out that you should not go on the retailer shop but directly in the office of importer of electronic components for the industry. Say that you are making prototype it works often and it's pretty fastThe problem here in BG is that there is no place where I can buy the proper ones, or if I could order I have to buy some 100 items, for example. In fact these are the components that the other 4 board are waiting for.
so try it
It can be used as long as your LPT port could drive the opto-couplers on the UHU board without requiring a buffer stage, most current laptops (that still include LPT port) use 3.3 volts interface, some of them will require a buffer stage.
Maybe the simplest way is to look for basic electronic courses at the nearest vocational school. It is probably better than the self-study because of the structured learning environment.The problem with electronics ain't in searching, but it is in "where to start from?" electronics are so vast, it's discouraging !
Any protection is better than no protection, your P6KE18 will clamp to about 17-18 Volts Vgs instead of 12-15 volts. Using the IRFP150N will limit your maximum motor voltage to about 50-60 volts.
Thanks for the reply kreutz !
My digital multimeter(dt-830b) reads 4.70 Vdc, but i measured it on the other end of my printer lpt cable it's 1.8m long so i think the cable is the reason of the missing 0.3 V, do you think it can work with such a long cable without a buffer stage ?
For begining electronics i found some Elektor basic courses (on the mule) do you think they are nice ? vocational school ain't enough flexible for my schedule !
Thanks a lot for your help !
cnc2.
Hi cnc2,
Your multimeter, having an input impedance of 1 megaohm cannot be the reason for your missing 0.3V. Nobody says that the 5V should be exactly 5V - there could be some variations above or below.
You could try to measure your 5V line directly from the power supply.
Todor
Thanks for the reply Todor !
Sorry man i was talking about LPT (// port) pins output voltage not a power supply unit, & i thought that my printer cable was acting like a resistor (it is 1.8m long) & was responsible for the missing 0.3V but i wasn't sure of my multimeter's accuracy but now i know it is 10mV resolution, what does it mean when it has 1 megaohm impedence input ? do you mean it's enough accurate ?
When i measure at my hard drive's power supply the mutimeter reads 5.03V (good tip thanks !)
Are the 4.7 V enough for driving UHU's optocouplers (now i measured at lpt port it is 4.7V output)?
excuse me if im not uderstanding i ain't good at electronics !
Thanks !
cnc2.
Last edited by cnc2; 04-13-2008 at 04:12 PM.
CNC2;
Logic level voltages are not precisely 5 volts or 3.3 volts, there is a voltage range for each logic level, having a no load voltage of 4.7 V means that your parallel port logic voltage is 5 volts based. It should drive the UHU opto-couplers without buffers.
cnc2,
The higher the impedance of a voltmeter / respectively the lower the impedance of an ampermeter/ the less influence it has on the circuit that it is connected to.
If you try to measure at the same pins but directly on the LPT port on the board you will see the same 4.7Volts.
The cable is not responsible for the voltage loss when you measure it as long as no load is connected on the other end. When there is a load the resistance of the wire takes place and the calculated loss is U=I.R . Since there are only 10-20mA at each pin there should not be a problem. Someone correct me if I'm wrong.
Todor
Right.
Thanks a lot kreutz, i'm really happy to be able to use an easier parallel interface for driving UHUs !
I allways thought electronics were precision mads, but i'm happy it ain't true for this case !
Thanks againe !
cnc2.
Thanks a lot Todor for that clarification !
You're right i measured on the port before printer cable & it's the same result.
I want to thank every body on the forum for the knowledge provided.
cnc2.
Hi all,
For those of you using UHU, can tou tell me the difference between UHU and UHU 300, is it the same PCB ? same BOM ?
Where can i get the latest project files for UHU ?
What is the best UHU PCB ?
What are the 0.1 Ohm 5W resistors used for on the UHU & is it possible to use 0.2 Ohm 7W resistors instead ? (couldn't find 0.1 ones)
Do you have a tip for reconizing a 24MHz fondamental crystal ?
Thanks !
cnc2.
The answer to most of the questions is at http://www.uhu-servo.de/servo_en/index.htm look for the FAQs.
Regarding to the best PCB I don't know.
You can use 0.2 Ohm 8 W resistors, depending on the PCB, the space to solder five of them could be really tight.
Talking about resistors for the original UHU board, nobody noticed that we replaced the five 0.1 Ohm 5 Watt resistors by two 0.02 Ohm 3 Watt resistors on the UHU HP board, and they don't overheat (Don't do this modification to the original board).
Kreutz.
Thanks for the reply Kreutz !
So, what i understand from your answer is that the 0.1 ohm 5w resistors are not used to lower the voltage but they are used to dissipate some Watts so the importance goes to the wattage not to the resistance, the resistance doesn't matter if the Wattage is at 5W ??? (what is the highest acceptable total resistance ?)
I found 0.2 Ohm 7 W not 8 W, is it giving the same result ?
What are thoes resistors used for ? are they used to lower the wattage that goes to an IC or a transistor to prevent it from heating or frying ? i saw some setups with 12 of them on other servo board models ???
(I saw the resistors are connected in parallel on UHU, from my basic course the sum of five 0.2 Ohm 7W in parallel will be 0.05 Ohm 35W it's more than the double of the original setup resistance with 0.1 Ohm resistors it is 0.02 Ohm 25 W total)
Is it a matter of resistance or a matter of wattage to respect ?
If i use say ten 0.2 Ohm 7W resistors then, the total resistance will be the same as with five 0.1 Ohm ones, ok, but if the resistors are 7W each does each resistor dissipate 7W continuouslly (70W total !!!) or they will dissipate the same wattage as the original setup but with less heating because they can handle a lot more Watts ?
Excuse me if i stick to this problem it's because i'm affraid to get a driver that ain't accurate & i won't be able to troubleshoot !
Many thanks !
cnc2.
Last edited by cnc2; 04-14-2008 at 10:01 PM.
Those resistors are really important in, value, tolerance, and power handling. The original design needed extra power handling due to extra high peak value current flowing through the sense resistors during cross-conduction. It is also necessary that those resistors have a very low inductance. Using higher power resistors than the specified will not hurt, using higher value will change the maximum current limit adjustment voltage value and will also increase the power losses on the current sense resistors.
On the UHU HP version we eliminated cross-conduction which allowed us to decrease the current sense resistor's power rating without problems. That is why I stated: "Don't try the same modification on the original UHU board".
Kreutz.
Thanks a lot Kreutz !
So, which is the best choice:
1)To try to find thoes resistors ?
2) Using the 0.2 Ohm 7 W instead ? (would you use five of them if you where me ?)
3) Building the HP UHU ? (does it cost a lot more than to build the original UHU) ? (does it require more skills to get it working ?)
Thanks !
cnc2.
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