Hello Guest it is October 15, 2019, 08:31:27 PM

Author Topic: MPG  (Read 5859 times)

0 Members and 1 Guest are viewing this topic.

Re: MPG
« Reply #50 on: February 02, 2016, 09:46:35 AM »
Thanks Overloaded, I will try it when I get back home and post the result.

Miso
Re: MPG
« Reply #51 on: February 02, 2016, 04:12:59 PM »
Here is another similar note from the Pokeys 57CNC manual ....


May be similar to yours.

Good luck,
Russ  :)
Re: MPG
« Reply #52 on: February 02, 2016, 04:49:01 PM »
I will try to connect a power supply first, and if that works, I'll try to trick to work with 5V one way or another. As it works for me  connected directly to the LPT, it's now more a principle that a need, I just want to get to the bottom of it...

Thanks for the info.

Miso
Re: MPG
« Reply #53 on: February 03, 2016, 02:31:12 PM »
Hi, I'm back and I've tried a couple of things as we discussed above:

1. Connected 12VDC to the external power supply terminals. This works. When I short GND and one of the switch terminals, the LEDs on the diagnostic tab react accordingly, But I'm afraid this is the only option that works, and it's not usable as is for what I wanted to do. Next thing is to try to trick the BOB, so it would work with 5VDC instead of 12VDC. The switch pins are connected to the opto couplers via the 1K resistors. I don't know if tweaking their values would help or not, maybe I'll try tomorrow, as I can't do it at home, too tiny for me;)

2. Next I connected USB cable, but this does't affect the outputs as 12V does. It seems to me it works exactly as when connected to the PC power supply. No changes on te diagnostic tab...

3, And now something I don't understand at all - if no power is connected (not 12VDC, nor USB or 5VDC from PC), I can still jog via keyboard and run the code...

This is a great BOB. Not only can it use wide range of voltages from peripheral and local sources, it even runs without an... Now that's what I call engineering;)

I have measured voltage on the driver terminals, and it is 1.9V. My guess (not that it's worth much) is that BOB gets it from the LPT port and that this is somehow enough, as when I unplyg teh LPT cable, there's no voltage on outputs.

Now my question is, even if I could use that ext. power connection, either tweak it to work with 5V or, theoretically, if I had 12V encoder instead of 5V one, how exactly would I connect the wheel to the BOB input terminals? I guess I can't just connect it like the switch, I would probably have to put some transistors on the switch inputs?

It seems to me it gets more and more complicated, given it already works connected directly to the LPT... But maybe it won't hurt to finish what I started anyway

Thanks,

Miso
Re: MPG
« Reply #54 on: February 03, 2016, 04:51:18 PM »
Hard to imagine this $10 BoB being so difficult. (on sale for $6 in quantity) :)

I would try it like this:  attached

Plug in the USB and check the voltage at the PC Power terminals, should be 5V (or maybe 3.3V  ::)) there.
Hook up A+ and B+ to your input pins.

Russ
« Last Edit: February 03, 2016, 04:53:59 PM by Overloaded »

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: MPG
« Reply #55 on: February 03, 2016, 06:13:40 PM »
First thing to say is I know very little about electronics but....

If the optos won't work with just 5v on the 12-24v input it will likely be because the resistor values are wrong for that low voltage. You should be able to look up the data sheet of the opto then use one of the LED/Resistor calcs online to work out what would be a suitable resistance for 5v and swap the resistors to that.

Hood
Re: MPG
« Reply #56 on: February 03, 2016, 06:52:45 PM »
Overoladed, I tried this first thing and it did not work, but I will try again tomorrow, as I think I did not plug the USB then, but +5V from the PC...
I agree, Hood. This is normal photo transistor optocoupler, shouldn't be  aproblem to tweak the resistors, but I can't do it at home, I can barely see the components, let alone soldering;) I'll take it tomorrow under the microscope, or better yet, bribe my friends to do it. I will post the result.
I'm attaching the datasheet, if anyone is interested.

Thanks,

Miso
Re: MPG
« Reply #57 on: February 03, 2016, 07:09:09 PM »
I see more clearly now. Looks like you guys are on a roll.
Thanks,
Russ
« Last Edit: February 04, 2016, 07:41:59 AM by Overloaded »
Re: MPG
« Reply #58 on: February 04, 2016, 12:05:42 PM »
I did not see your image before, but it's correct, I used .47K instead of 1K and everything works fine. Thanks.

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: MPG
« Reply #59 on: February 04, 2016, 12:18:51 PM »
Good you got it, only thing I can see as being a possible problem now is if you wish to use the boards 0-10V for controlling a spindle drive, most likely that will require the 12-24v input and you will only have 5v.
Hood