[ger21]

Mike, if you're worried about the parallel port, just add a $20 PCI parallel port card and use that port.

[Mike F]

Gerry,

Not sure I understand. I thought the idea of opto-isolation was that any extraneous signals could not find their way into the computer via the parallel port. Surely by adding another, it still provides a pathway into the computer? or am I missing something? Is a PCI parallel port already opto-isolated?

Mike

[rboeser]

Hello Mike; What Gerry is saying is you can purchase an additional parallel port and install it in an open PCI slot on your PC. This way if for some reason something goes wrong you blow up a $20 add on card, not your motherboard. There are no promises that it will only kill your add on card, it may continue further and kill other things on your motherboard, this is however cheap insurance to protect against it. It is better than using the "onboard" motherboard parallel port as you will surly kill a motherboard with a "direct hit" if something went wrong in your CNC control box.

Not all break out boards are opto isolated. You should really save the money and buy one that is, it will save you problems later. From memory, the Cambell BOB looks really good, and he will help you with questions if you email him. I'm certain there are other good BOB's that are opto-isolated also.

[Mike F]

Thanks rboeser, I understand now.

The CNC4PC parallel interface card I ordered was in fact the opto-isolated one but the wrong one was delivered and rather than the hassle of return packaging and the wait to and from the USA and UK, I have decided, after some invaluable help from my local electronics expert, to continue with the one supplied. I was just trying to gauge the chances of doing some serious damage to my PC.

Cheers,

Mike

[rboeser]

You are welcome, please stay safe.

[Mike F]

Attached are pictures of the control box and all the bits that have to be stuffed inside. I am sure I will find a more elegant way to insert them rather than stuffing but you get the idea.

I am not sure whether to put the Geckos, with their attached coolers on the front panel, back or sides. Does anyone have any advice on this? I quite like the idea of having them on the front for 'Technical' aesthetic appeal but am worried that there is more chance of dust ingress than if they were mounted on the back or sides when the whole box is housed in a cabinet. I am well aware that whatever the method used, I will have to ensure adequate ventilation all round.

Just got to find a bigger capacitor now as the one shown is only 10,000uF @ 40V.

Another question if I may, what indicator lights/LEDs, switches, fuses etc. should I have on the front panel? I would like to get this as right as possible first time.

Thanks,

Mike

[Mike F]

I really could do with some answers to the previous post.

There must be someone out there who has built a control box only to find they should have included another indicator, switch or whatever on the front panel. It would be a shame if I had to make all the same mistakes. After all, is'nt this what this forum is all about, sharing ideas, mistakes, highs and lows?

So far, the forum has been extremely helpful and I could not have got this far without it. Just a bit more help pleeeeeease so I can get on with the control box happy that I have not missed something obvious.

Mike

[jjwl89]

Hi Mike

I'm not sure if you are still in need of a reply but seeing as no one else has responded, I might as well share what I am planing to do with my contol box. First, I would suggest a main power switch. This will control the AC power to the big transformer and power to the control power supply you have. Then, I another power switch controlling power from the smaller control power supply. If you want you could put leds with the correct resistors for power indication. As for fuses, I would use resetable breakers. The make them panel mountable and in many different ratings. This way, if you blow one, you don't have to replace a fuse. I know Mouser Electronics sells them but most other electronics places have them too. A main power breaker and a breaker for each gecko should be good. (However you might need them in other places). It looks like you have the safety charge pump from CNC4PC so you will need an override switch for this so that the breakout board can be powered to send the signal to the charge pump. Also, if you are going to be controling your gecko's err/res state, you will need a SPDT momentary toggle swith to engage and disengaged the drives. A fault led can also be installed to monitor the state of the drives. Look in the gecko manual for information about controlling the err/res pin. Finally you may want to have an e-stop button.

I would suggest mounting the geckos on the side of the enclosure. This way you minimize the dust intake and you can have room for rear connections. Also, for good air flow and to prevent overheating, make sure you have enough intake fans to keep the pressure equal inside and outside of the box.

On the back, you are going to need an AC power input. And, since you have a solid state relay board, you probally are going to want to have AC outlets to plug your spindle motor, coolant pumps, etc. into. Finally for connection to the servos and encoders, I would suggest circular connectors. These look cool and provide a good conncetion between the cable and your box. Make sure that all of you cables are sheilded and that the drain wires are all connected together within the box to avoid ground loops.

Hopefully, this will help you.

[Apples]

Mike,

I have found where you can get yourself a larger capacitor to use. It is from the altronics website. Rated at 10,000 and 100vdc, i think from memory about $28AUD. I am going to use one of these myself.

Cheers

Peter

[Mike F]

Jason,

Many thanks for that - I thought for some time that my thread had become invisible As a complete electronics novice, I really do appreciate the input and had put off doing anything on the control box until I had some feedback.

You mention circular connectors for the outputs to each of the servos and encoders, can both be put together on one connector? Wouldthere not be problems running the two alongside each other? I thought I had read somewhere that encoder cables should be kept as far away as possible from the servo cables. Presumably this is what the shielding is for?

Not quite sure I understand the need for the override switch for the charge pump.

Peter,

Thanks for the contact but postage from Australia would probably double the cost. I am sure there must be somewhere over here I can purchase a capacitor that size.

Thanks again for the much valued input,

Mike

[jjwl89]

Hi Mike,

I Dont think that it would be a good idea to out both the encoder and servo connection in one connector. The encoder signal may be interfered with due to the servo signals. Shielding prevents crosstalk in the cable, but if you are using plastic connectors, they will not shield from crosstalk within the connector. I mentioned circular connectors simply because they provide a secure connection and they look good. I got the idea from cyclone's box which you mentioned before. You could use any connector as long as there are enough pins (including one for a shielding drain wire) and that they can handle the current of the servo motors.

The saftey charge pump bypass switch is something in the CNC4PC instruction manual. It simply bypasses the saftey charge pump momentarily (Push button or similiar switch) to allow power to the breakout board so that the signal from Mach 2 can get to the saftey charge pump switch to enable the system. I have attached an image from the instruction book for the saftey charge pump.

[Tompie]

Hi,

This is a very interesting project I will follow the progress.
Keep up the good work.

Tom

[DOMDEC]

Hi,

I was just wandering, why do you want a bigger capacitor then 10000 uF.
That is already a big one, or are looking for a higher voltage ?
You can always connect several capacitors in parallel to get a bigger capacity. (There are some real nice ones in frequency inverters, if you can get hold of a broken one).

From what I see by dismanteling machines is that for smaller servo motors they generaly do not use shielded wires for the power supply, however for the encoder you must as these are very prone to magnetical fields.

And indeed you best use some metal connectors.
Get some robust items as they are subjected to swarf of wood and metal particals, resonance and quite some abuse by moving parts of the machine.

Good luck with your project.

[Mike F]

Domdec,

As a complete dunderhead, when it comes to electronics, I can only go by the experiences and expertie of others and the general concensus seems to be that for my 36V x 20amp system, I need a 56,000uF capacitor. I don't pretend to understand the maths behind solution or, indeed, the science

Again, the beauty of this forum.

Mike

[Mike F]

OK, now for a couple of technical questions posed by my electronics friend who is helping me out with my control box.

1/ In the Gecko manual it shows a centre biased, three way switch used to enable/disable the drives. On HomeCNC's (Jeff) instructions each of the drives are wired to the same switch. Question 1 - If I have indicator LEDs on the front panel for each of the drives, surely all will come on when any one of the three faults, if so how do I know which drive has faulted? Question 2 - If pressing the switch one way arms the drives and the other turns the drives off is the off position not the same as an emergency stop? If this is the case surely it would be fairly simple to catch this swtch accidentally and turn all the drives off - Does it have to be connected?

2/ Which side of the power supply should the emergency stop be? Should it turn power off to everything, in which case it can be put in the supply line or, should it only stop power to the servos, in which case it can be placed on the Gecko ERR/RES pin?

Thanks in anticipation,

Mike

[Kenwood714]

Mike

The err/res terminal has been somewhat vague for most who approach its use. It is needed to reset the drives only. What you do with it from there is up to you. The stop function I use for a hardware stop and the EStop switch is a software stop. I can turn the drives off without alarming the software. You can go with a 3PDT switch to reset and stop the drives if you intend to use LEDS for individual drive condition indicators. The Gecko manual shows you a small circuit for this purpose. If you use Jeff’s circuit then you only need one LED for error indication. When you tune your motors and set up your drives you will be looking at the drives and will notice any error. Once you have them set up properly they should not error so having the indicator may just be extra effort on your part. The easy way is just wire the switch as Jeff shows. There are fancy boards out there to handle the err/res terminal and if one drive errors it will shut down all three as well as auto reset. I have seen circuits shown here on the zone as well if you feel up to making the circuit boards. But from what I have read you may want to take the keep it simple approach. If you want to get rid of the switch completely just tie the err terminal to encoder b+ and leave it that way.
The EStop will just be a switch that wires into your parallel port interface board and can be configured by your software. The easy way is to have it ground the pin on the board to make your software stop sending step pulses to the drives.

Ken

[acondit]

Ken,

I am puzzled. I would have thought that an E-stop was an emergency stop and as such that it would be an immediate hardware stop. Am I missing something?

thanks,
Alan

[ger21]

Ken,

I am puzzled. I would have thought that an E-stop was an emergency stop and as such that it would be an immediate hardware stop. Am I missing something?

thanks,
Alan

No. The correct way to use an estop is for it to cut power to everything. Not just have it stop the software. Usually they have 2 sets of contacts so you can do both.

[DOMDEC]

I am afraid it is a little bit more complicated.

The E stop with servo driven motors schould send the message to the drives to that there is an emergency.
The drives should then boost the motors to a stop (as quick as possible) and after that releasing the axis (let it be posible to free run). But what about a Z axis that can drop down ?
At the university I am working at we have people teaching couses about technical security and there is something as a safety guidance to machine desing (European normalisation). Heavy stuff.

Do not cut the power supply but the lines between the power supply and the spindle motor (if applicable) (or make them quick stop by electrical braking) and in worst case cut the power line (by contactor of couse) to the servo drives (if they don not have a inboard breaking system) , otherwise follow the manufactors guidline.

Hoping to solve this together

[Mike F]

Thanks for all the responses.

It still seems a little complicated and somewhat confusing but if I can assimilate all the information, it looks like I need the emergency stop to cut power to the spindle (preferably with electrical braking) and to turn the drives off via the err/res pin. Presumably by doing this the servos will hold position and therefore the Z axis will not drop?

If this is correct, for the Gecko/servo application using Mach2, how do you then safely move the axes? Is this something that is set up in Mach2 so that when it sees a reset, all axes are homed by zeroing Z first then either X or Y?

Some progress has been made on the control box, just waiting for all the plugs and sockets to arrive.

Mike