Do you hate the current set resistor?

[Mariss Freimanis]

Step motor drives need to have their current set to the motor being used. For 10 years we have opted to use a Current Set Resistor. There are other ways of doing it and I need your input on what you would prefer.

1) Current Set Resistor.

Pros: A $0.05 part sets the drive to the desired phase current. Easy to set when you use a lot of drives; use 1,000 drives, get 1,000 resistors. Put them in place and 1,000 drives are programmed.

Cons: You have to find a vendor for the resistor. Not an easy thing to do in many places especially if only 2 or 3 drives need to be set up. Cheapest solution.

2) Trimpot Current Set.

Pros: No extra parts needed. Put a Voltmeter on some test points, turn the trimpot to set the current. 1V equals 1A per phase, 7V equals 7A per phase.

Cons: You need a Voltmeter. You need to put it on test points. Some time later someone sees a trimpot and he turns it. Sets the current all wrong and burns the motor down. 3rd cheapest solution.

3) DIP-switch current set.

Pros: No extra parts needed. Set the switch settings to the required current.

Cons: 6 switches have to be set to the correct pattern. The pattern has to be looked up in the manual and it's easy to get mixed up. Use 1,000 drives and you have to set 6,000 switch settings. Most expensive solution.

4) Jumper headers.

Pros: Just like (3) except you set 6 header shunts. 2nd cheapest solution.

Cons: Just like (3) except setting 6 header shunts is a bigger PIA than setting 6 switches.

We are revamping our entire product line. That means redesigning all our standard drives to use CPLDs. The attached pic is the G201 replacement called the G201X. It shows an alternative current set using a DIP-switch.

Mariss

[acondit]

Mariss,

I actually like the current set resistor, especially the way you implemented it on the G250, G251 drives. I like the idea of being able to put the resistor on the motor plug and change motors without opening up the drive.

Alan

[MrWild]

It boils down to who is your biggest customer? The cheapest solution works well on all drives except the G540. Problem with the G540 is the design concept doesn't allow big clunky jumper arrays or pots. Once someone starts making cables, the only bottle neck to plug and play is pretty much over.

The idea of tossing a set of set resistors along with each single drive seems like a good one and would keep folks from needing to run out in the middle of the night hunting for the right resistor but allows mistakes in the selection. The set of set resistors would only be sent in the small lot packaging, but way too easy for mistakes, so the thought process of needing to go buy them may keep down the returns.

If you sell more drives in large quantities, then it is up to those guys, and the time it takes to mount in their equipment. Short time to spin a dial, longer to tighten two screws. I doubt the thought of someone down the line spinning the dial on a drive locked in a box will cause them to not like the pot idea.

One question though. Why is a voltmeter needed? Is it possible to just have a numbered dial you spin to the number for amps?

[CoAMarcus]

Alan,

The can would have a hole cut in it to accommodate the DIP switch for the current set. You would not have to remove the can to set the switch and it would be very simple to do. The same would go for the trimpot and jumper ideas.

Marcus

[dertsap]

i like the dip switch idea

[Richards]

Why not pre-install a current set resistor at the factory for those customers who specify the current rating of the stepper motor that they are going to use?

[TOTALLYRC]

I would say that the g540 as it is currently set up is fine since it allows the drive to be moved form one machine to another just by swapping cables with the appropriate resistors in side the db9 shell.

On the other drives, anything that is going to require a voltmeter just makes it more complex and prone to error.

The other option is like the curent set resistor, but it is plug and play.
Similar to how rpm limiters work. You get a nice "chip" will call it and it is labeld in the amp rating you need. Even if it is just a resistor inside a nice housing. When you buy drives, You get a bag of them with each drive. I would think that they should be available in .5 amp increments. It would most likely be too expensive to do, but I can dream can't I????

You say that a pot will be fiddled with, burning out motors, but you could say the same for dip switches, and dip refers to the people who will fiddle with anything that they are not supposed to, not the type of switch.

Jumpers, in the size that they will have to be to fit inside the case, will get dropped inside the drive or lost, so they are more problematic than first mentioned.
Might even require needle nose pliers to manipulate.

How about a rotary selector switch, which will not need a voltmeter to setup and could also be in .5 amp increments. Just pick the setting that is closest without going over. Again probably too expensive.

Of course, just including a bag of resitors like mrwild said sounds great, but the logistics of it might be too expensive, depending on what the resistors cost and who has to bag them, and then toss them in the box for shipping and so forth. I am pretty sure that all of your drives are smt so you probably don't even use these size resitors in the production process anymore.


For most drive owners, that use a bunch of drives, the amp setting is most likely a one time deal, but many hobbiests will make a change once in a while to either move to a different machine, or try different motors.

Just adding to the confusion is my speciality, just ask my wife.

Mike

[jimbo7]

I like the dip switch idea. For the G540 I would agree the current method of placing the set resitor in the connector is OK. The problem with the G540 way of putting the current set resistor in the cable connector is that for higher current drives the connectors become more expensive, as they need an extra set of contacts plus the time to put these into place. Also, you would need to silk screen the switch setting diagram on the drive or provide a sticker label to attach near the drive.

[PEU]

can I offer a 5th alternative? why dont you sell sockets like car fuses with resistors in them?

brown=1A
red=2A
orange=3A
you get the idea




Then the user picks the right color for his needs, plugs in and its good to go, cheap, easy and fast. You could sell singles or a whole kit.

Make them different shape than car fuses to avoid confusions.



Pablo

[ger21]

I vote for DIP switches or Jumpers. Either would be fine for me.

[Adamj12b]

I have a few questions before I make a decision. What is the resolution of the dip switches/jumper headers? For the trimpot, Would the test points be accessible without opening the cover? Would the current value set by the jumpers/dip be digitally controlled? Or, Would it just switch a series of resistors to create the value needed?

As for a socket resistor, I like the idea, But I think that it wouldn't be practical. You would need to order special resistors that could take a week or more to come in. If your in a hurry and need to replace one that you dont have a spare of...

The best solution would be something that is built into the drive, you never need anything extra to make it work. I know that when I got my 251's I looked through my box of resistors(hundreds), and didnt have one close enough to the value of what I need and had to get more.

I think that is it for now.

-Adam

[High Seas]

Dip Switch and pass the cost along.
Makes for the easiest Plug-N-Play.
Marine electronics, chargers and monitor/controllers have opted for the dip switch as the simplest way to let the user set it up.
Sure, a package of fuses included in the box would save hunting for the right bits - but a simple dip switch makes it easy-peasy.

Cheers -- and thanks for asking!
Jim