[ger21]

Comments please.

Mariss

Just a guess, but I think that the majority of people purchasing this unit will not be using VFD's, and would prefer having an extra output pin available.

Although having the ability to control a VFD built in might entice more people to start using VFD's.

[Crevice Reamer]

I LIKE the VFD controls. How many outputs does that leave me with?

CR.

[Greolt]

At the moment it has four general purpose outputs.

VFD control certainly gets my vote (for what it's worth)

I'd be more reluctant about losing that extra input. (fault signal)

Greg

[phomann]

G540 next revision (REV 2). I took some of the advice to heart and added a few additional goodies:

1) DISABLE will be renamed ENABLE. The ENABLE input must be shorted to GND to enable the G540. If ENABLE is left open then the G540 shuts down.

2) A watchdog timer (charge pump) is added. No 25kHz on the DB25 pin 16, no run.

3) The +5VDC input from the PC is eliminated. An isolated internal DC to DC converter coughs up the +5VDC at 10mA need for parallel port input pullup resistors.

4) Two general purpose outputs are eliminated, serviced by DB25 pins 14 and 16 in the current G540 REV1. Pin 16 is now the dedicated "charge pump" output and the use of pin 16 is discussed next (5).

5) An optoisolated VFD interface is added. The interface uses 3 terminal positions; VFD +V, VFD -V and VFD OUT. This circuit is completely isolated from the rest of the G540 to a minimum 300V breakdown voltage.

My understanding is most VFDs provide a remote potentiometer connection of 10VDC at 10mA. VFD +V goes to the '+' side of the pot connection, VFD -V goes to the '-' side and VFD OUT goes to the pot wiper or input connection. The output voltage range is from 0V to whatever '+' is (this must not be more than +12VDC). The VDF signal must be a PWM output on the DB25 pin 14. The -3db bandwidth is 5Hz.

6) A FAULT output back to the PC has been added. This output reads as a '1' when the G540 has faulted out (shut down) due to a short-circuit on a motor lead or when the ENABLE input to GND is disconnected (E-Stop). It is on the DB25 pin 15.

7) Internal ultra fast blow fuse protection. This is to help with the power supply polarity reversal thingy.:-)

8) We will be including 4 mating male DB9 connectors (solder cup type) and 4 sets of DB9 connector backshells with each G540 to ease the user's motor cable fabrication work.

Comments please.

Mariss

1) Sounds good. One of the uses for this pin is to manually disable the drives, so that the axes positions can be tweeked by hand. This is not always desirable to have Mach see this as an EStop.

2). Not sure why you chose 25KHz? I think that the standard chargepump frequency is 12.5HKz. Maybe it is now configurable. Also, you should consider providing a jumper so that the system can operate with a logic signal rather than a frequency (Not all software can produce a charge pump).

3). :-) I have always failed to understand why BOB manufactures don't do this, relying on the user to supply another powersupply source.

4). OK

5). VFDs usually have a +10V 10-20mA supply for this purpose. The more common and cheaper speed controllers that will most likely be used with the G540 do not. They use a Zener diode shunt regulator to provide power for the manual Potentiometer.

The kicker is that they can only supply a few mA, certainly not 10mA. Basically, just enough for the 5K pot (3mA), even less possibly for those designed for a 10K pot. If you draw more than the 3mA, the supply to your converter circuit will sag (the amount of sag varies with the active impedence of your circuit. The result is a non-linear speed response and a reduced maximum speed -Not good)


Also, most of them provide 15Vdc such as the KBIC-120 controllers as used in the sherline products, so your 12V limit will not be sufficient. Many of these controllers can be controlled via a 0-10V signal referenced to the -ve pot terminal. Some still need the pot (or a resistor) attached (without the wiper connected).

Basically, the bottom line is that for reliable operation, you need another dc/dc converter (12V-15V), suppling the isolated circuitry rather than relying on the speed controller to provide it.

The Digispeeds DC-06, now have an optional plugin DC/Dc converter for this purpose, If it is to be used with a VFD the converter is not needed, but for cheaper controllers it is recommended.




6). I don't know if you have addressed it, but make sure that you avoid a race condition between the fault input and the chargepump. If the chargepump is not present the fault is activated, which disables the charge pump, which activates the fault line........


7). Good

8). Good.


Well you did ask for comments.... :-)

Cheers,

Peter.

[Mariss Freimanis]

CR,

A PC parallel port has inputs as well as outputs. The inputs require power to drive them. This power (5VDC) must be grounded on the PC side of the optoisolator interface. That means (a) steal 5VDC from somewhere on the PC (a real pain in the rear) or (b) generate the needed 5VDC using a transformer isolated DC to DC converter inside the G540. The REV2 circuit includes a 100kHz 5VDC at 20mA isolated supply.

Jason,

Same price and I no longer do ETAs except to say the new board was sent in for a 5-day turn prototype fabrication 2 hours ago.:-)

Mariss

[CROSSHATCH]

Oh wow! So it's possible it can be done in a week or two. I'm still debating too wait...I may, We'll see how it goes.


-Jason

[Mariss Freimanis]

Peter,

Excellent points.

1) Good point. I'll see if I can add the necessary OR function.

2) I wasn't aware it was 12.5kHz. No matter. This is an interesting circuit in the G540. The opto LED current limit resistor (200 Ohms) is in series with a 100nF for an LED 'on' time of 20uS. The collector side load is such that the phototransistor is deeply saturated to insure a very long (100uS) storage delay time. The collector output is low-pass filtered (10mS) such that any frequency below 5kHz is interpreted as '0' while any above that is a '1' due to PMWing on the collector. Spurious activity on the input would have to last 10mS to be 'seen'. It uses the miserable frequency response of a phototransistor to good advantage.:-)

5) The VFD circuit consumes 800uA of current worst case. It has a Miller-Effect canceling front end (100kHz BW) to speed up the photo-transistor which consumes 600uA all by itself. The rest of the circuit uses a rail-to-rail dual CMOS op-amp 3-pole Chebychev active low-pass filter having a 5Hz -3db cutoff.

Mariss

[Crevice Reamer]

3) The +5VDC input from the PC is eliminated. An isolated internal DC to DC converter coughs up the +5VDC at 10mA need for parallel port input pullup resistors.Mariss

Hi Mariss. I understand perfectly about the 5 volts. I was trying to tell you there is a confusing typo in number 3. On further examination, I think you meant to say "... 10mA need(ED) for parallel port input....."

CR.

[Mariss Freimanis]

CR,

"Prototype" means I get precisely 5 printed circuit boards (minimum order from the proto board house) at $33 each in 5 days. One will be populated and tested. The other four get thrown in the trash directly from the UPS package they were delivered in.

Mariss

[CROSSHATCH]

Or you can just send all 4 too me and I'll throw them away....:P lol



PS, I calculated that my steppers would need 7.5 amps altogether, if I ran a Max 7.3 Amp, because thats all the Kelinginc PS will output, will I be ok? Or am I cutting it too short and losing efficient power?

This would be in a Bipolar (Parallel_ configuration (For best performance, I think).

-Jason

[Mariss Freimanis]

Visit the trash bin behind our shop. You will find far more interesting things in it than just bare printed circuit boards.:-) My shop policy is to never accumulate things no matter how cool they are if they are never going to be used. Keeps the clutter down. I hate clutter because it camouflages what I'm looking for when I need something.

Mariss

[CoAMarcus]

Missing 200mA should not affect anything too badly. You will be getting a little over 97% of the performance you would otherwise get with 7.5A.

Marcus

[CROSSHATCH]

I will jump on a plane and googlemap your freaking shop, then I will search your garbage. NO really, any insight on my ABOVE question?


-Jason

[yngndrw]

Visit the trash bin behind our shop. You will find far more interesting things in it than just bare printed circuit boards.:-)

How I wish I could.

Sounds good, maybe you could keep all of the outputs and have chargepump / VFD inputs on the connector block ? This way outputs could be looped back into the system if needed.

[wolfdagon]

Sounds great. Especially at the same price. Now I don't feel quite so bad that I can't get one right away.

Kenith

[Geckomia]

Hi,

I am new here and just wanted to say Hi to all the members.

Maybe I can learn how to do what you guys are so good at.

There is so much here I don't know where to start.

[joeybagadonuts]

Anyone selling D251 Gecko's?

JoeyB

[edferg]

G540 next revision (REV 2). I took some of the advice to heart and added a few additional goodies:
Comments please.
Mariss

Any chance of a low cost mother board exchange later for us early adopters?

I purchased a G540 today because I need it now - but the new goodies would be nice to have later.

Ed

[tauntdesigns]

Hey Guys,

I received the G540 and it is small. I saw the pics of it next to an x-acto knife, but it didn't really sink in.

I'd like to ask a few questions, but thought I should ask in a new thread.....
I thought I'd title it "G540 questions" thinking others could also use the thread for their questions. (keeping info together)

Any thoughts on doing that?

Cheers,
jack

[CoAMarcus]

Any chance of a low cost mother board exchange later for us early adopters?

I purchased a G540 today because I need it now - but the new goodies would be nice to have later.

Ed

Ed,

What we will do for those who request a new motherboard is send them one free of charge to replace their existing one. It will be a fairly simple install, and you can then do as you like with the existing REV-1 board. I know I am not a fan of being an early adopter just to have a better or bug-free version come out just a little bit later (e.g. the iPhone) so we try to minimize the irritation that some may feel. All we will need is for those who bought the current G540 to call us, email us, fax us or send a carrier pigeon to ask for a new motherboard.

Hey Guys,

I received the G540 and it is small. I saw the pics of it next to an x-acto knife, but it didn't really sink in.

I'd like to ask a few questions, but thought I should ask in a new thread.....
I thought I'd title it "G540 questions" thinking others could also use the thread for their questions. (keeping info together)

Any thoughts on doing that?

Cheers,
jack

Jack,

I think that may cut down a bit on the clutter of this thread for someone looking for specific questions to be answered without having to search through all these posts.

Marcus