[hhogendoorn]

You can program the pic "In_Circuit", if you search for example Microchip AN851 sheet 20 you see a MAX232 connected to pins 25 and 26 of the 18F452.
together with the free MPLAB software and a serial port on your pc it's possible to program the hex file.
Please do not remove C5 an C4 , it's necessary for decoupling.
The Backlight serial resistor is +/- 82 Ohm.

Hans

[MGTp93]

Sorted it. Only had to isolate pin 1 (cutting the vdd trace near it) and connect it back to vdd through a 10k resistor, then made all connections as shown in pic and programmer documentation(s).

Just had some errors where MPLAB IDE couldn't id the chip, the reason was i had quite a few small interruptions on the pcb, at those fine traces, one even on the pgd line. I patched the pcb and thickened all of those fine traces, then programming worked like a charm. I will continue when i get the other parts, just for now chip seems to be ok.

[joegib]

Hi,

Can I raise the vexed question of suitable drives/stepper motors again, please?

I imagine this excellent project appeals to a lot of people like me who've no intention of getting into full-blown CNC but who would like to exploit modern electronics to automate some tiresome manual engineering processes like dividing. Personally, I don't expect constructing Steve's control unit to be a problem and, likewise, I can cope with the mechanics of hooking up the stepper to the the dividing head I plan to use. Where I'm all at sea is in specifying/obtaining a suitable drive and stepper motor.

There was some discussion of these matters on pages 15/16 of the thread (post 174 onwards). That gave me some idea of what to avoid (the cheapo Chinese drives offered by many traders on Ebay). I'm still fuzzy, though, about what kind of torque spec I need for the motor. I appreciate this depends up to a point on the duty required.

So, can I ask people who've built Steve's project to drive 4 - 6 inch rotary tables of the kind used by home workshop guys (Vertex and suchlike), what torque spec does your motor have? It would also be helpful if people with some expertise in these matters could say what the minimum torque spec for this kind of duty would be.

Thanks

Joe

[gandalf1]

OK second attempt at posting, first has vanished into Cyberspace.
Firstly may I add my thanks to Steve for posting all the details for building this piece of equipment. Next I would like to ask if anyone has had experience of using the latest version of software in which it uses motor steps per chuck or table revolution as I am using a 36:1 ration worm and wheel gear set and 200 step motor? I spent a most pleasureable evening going through all the posts on the project but could only find a single reply as to how well it worked. Also for my own convenience is there a DFX drawing or set of GCode I can use so that I can mill the circuit on my home brew CNCRouter?
I ordered the display from China and for those in UK the PIC from Saltburn on Sea so now am awaiting anxiously the delivery from the Far East although most likely the local delivery will take as long. In the meantime I can make a Nema 23 motor mounting bracket to attach to the little dividing head I am, converting and continue collecting the rest of the controller components.
Thanks again Steve for the inspiration to convert my dividing head.
John.
PS Perhaps in recognition I should print out a Duck logo and stick it to the control box.

[kwackers]

Hi John,

It's probably a bit 'off' for me to answer your post but perhaps I can allay your fears. ;-)

Firstly 36:1 and 200 steps will work fine with either version. The older version of the software makes an assumption of 400 steps so you'd need to fib and tell it that the ratio is 18:1 instead of 36 (since 36*200 is equal to 18*400).
However I'd suggest you run the motor in half step mode (you should be able to set your driver up for this) in which case your motor will be 400 steps.

If you use the later version of the software the only thing that has changed is that previously when the ratio was entered it was multiplied by 400 and stored. Now you enter that number directly which is why we can have strange ratios that weren't previously possible.

Hope this helps.
Regards Steve.

[gandalf1]

Steve,
I can think of nobody bettwer qualified to answer my question so quickly. Now I have to decide which way to jump, at the moment I cannot think of any odd divisions needing other than those divisible by 2 but there may come the time when I need an odd number of teeth on say a toothed belt pulley so p[erhaps the latest version is best for me. Pity the pension does not run to more than one PIC or else I could swap things around a bit. Of course not having used these things before that might not be possible. Sadly my motor controllers only support single stepping which is why I thought to ask first before I considered adding a 2:1 belt reduction into the system.
Thanks for your quick reply.
John.
PS For those interested the PIC 18F452 from mechanique.co.uk in Saltburn the cost was £10.90 including postage

[kwackers]

Hi John,

You may as well use the later software, it's identical in every way with the exception that you need to multiply the worm ratio by the motor steps before entering the number, since this is done once only on setup and gives you the versatility to easily move the device to another piece of division hardware with an oddball ratio sometime in the future then there doesn't seem any reason why not.

I'm slightly confused by your post though and think it's possible you've misunderstood how the device works?

Just to clarify. The number you enter in the setup is simply the ratio used by your dividing hardware. Once this is entered you never change it (unless you change the hardware).
When using the software you can tell it how many divisions you need directly, e.g 7, 16, 537 etc etc.
This is identical on both versions of the software and doesn't require the setup to be changed.

So for example, if you want to divide by 19, you turn it on, select division and enter the number 19, that's pretty much it.

Steve.

[gandalf1]

Hi Steve,
Here on the edge of the East Angular Fens we may sometimes get a little muddled. Buzzing around in my head was something about only being able to divide in multiples of two anyway you have set my mind at rest so I'll now start making bits. First since it is easiest an adaptor to connect my motor to the little home made dividing head and then on to the circuit board.
Thanks for your valued assistance on the project.
John.

[gandalf1]

Hello again Steve,
A thought occurred to me about the uses for your controller. I searched the documentation as best I could but although and found there is a continuous running command. Is it at all posssible to add or is it already included a command for a number of output turns. I have in mind something to instruct say a milling machine to move the table a set distance which would require a number of turns rather than continuous rotation. Maybe I have got it wrong but it would be useful for me to be able to move lathe saddle or crosslide, mill table or even adapt the bench drill pre-determined distances.
Sorry to be a pain yet again.
John.

[kwackers]

Hi John,

There's no trivial function to do that, you may be able to use the program mode to 'hack' something.
One of the biggest issues is the calculation of distance - you'd need to be able to figure out what the displayed angle meant in terms of distance. It may be possible to arrange gearing so that 360.0 was 360mm or 36 inches etc. You'd also then have to watch out that it didn't 'loop' - i.e. because it assumes it's driving a rotary table it thinks it can get to (say) 1.0 from 350.0 by moving forward another 2.0 units...

In simple terms it was only ever designed to replace a set of dividing plates and being digital it can divide quite happily by any and every value from 1 to 9999 (including primes).
Whilst there are many possibilities for a linear version, the work I've done on looking into it shows it to be a much more complex area requiring a fair bit of my time to get anywhere with. I do have software partly written for a linear version but currently just don't have the time to do much on it.

Regards
Steve.

[Khalid]

Steve,Excellent programming and electronics combination... You must be proud of your inventions..and utilizing your skills can make you do some unbelievable projects..You are the man...

[Khalid]

Steve,
All things are working fine here except a minor issue... My LCD display is blinking (The backlight LED) .. This causes bad effect on display, however display is very good readable... Did you program the LCD like this?.. Is it the Refresh rate or something i have to adjust the POT?
Regards

[kwackers]

Hi Khalid,

The backlight for the LCD has nothing to do with the controller. It's simply fed from a resistor ("Backlight" on overlay - not shown on circuit diagram) via the 5v line.

If it's flashing, then I'd think it's either not intended to be run from 5v via the resistor or there's a fault with the LCD.
If you have the datasheet for the LCD you purchased, might be worth looking at that to see if it can cast any light on the issue, failing that swapping the LCD is all I can suggest.

Regards
Steve.

[Khalid]

Thanks Steve,
I am using LMB204BFC Lcd display from Topway.. Attached is the spec. sheet..Can you please help me resolve the problem?

I am using 2.11 Firmware and all the functions working perfect..The only problem is flashing of LED's of LCD...

[kwackers]

I can't see anything unusual about the display, looks pretty normal. (The backlight circuitry looks as if it might have it's own current limiting resistors already).

The only thing I can suggest is separating out the backlight supply. Disconnect pins 15 & 16 and run them through a new resistor to the power coming into the board.

Your docs show a vFwd for the backlight of 5v and a max current of 80mA. If we limit the current to say 50mA to be on the safe side then we can calculate a resistor (ignoring the resistors shown since we don't know what they are).

Using the formula R = V/I, where V is the supply voltage minus 5 and I is the 50mA.

So say your supply is 24v, then R = (24 - 5) / 0.05 = 19 / 0.05 = 380 ohms (or nearest value you can find).

Bear in mind power loss in the resistor is given by P = V*I, or 19 * 0.05 = 0.95W
So the resistor would need to be at least 1W.

[redpiperbob]

Hi Kwackers
can you tell me if the K8076 - PIC Programmer Board KIT can programme the pic 18f452 chip. I have emailed the makers but have had no reply. While I am on thank you for all your hard work.
Bob

[Khalid]

Thanks Steve for advice and calculating the resistor value...,
I will try to install new resistor and will show you the results...
I am using 12Volt logic supply (Resistor: R140 1/2Watt)to your controller and will use Gecko 203V drive with seperate supply 48V to run a stepper motor 600 Oz-in 4A 1.8 degree per step.. I dont know how the G203V will handle the step and direction signal from rotary indexer controller.... This is because the G203V itself has specially designed 10microstep and i dont know how will it behave...

[kwackers]

@redpiperbob. I'm afraid I know no more than you, I googled it but the 452 isn't shown in it's list of supported devices so may be best to assume not.
There are many cheap programmers available on eBay (usually from the far east) that are available (search for "JDM programmer").

@Khalid
Just one point with regards your driver, the maximum number of steps my controller can issue per full revolution of the table is 65535. When microstepping you may find the number of microsteps required to rotate the table exceeds this. I would advise only using half stepping if it's available. For this application there is nothing to be gained by microstepping.

[Khalid]

@Khalid
Just one point with regards your driver, the maximum number of steps my controller can issue per full revolution of the table is 65535.

Hi Steve,

At What KHz your controller work?... Considering G203V is 10microstep drive with 40:1 gear box and 200 step motor then, 40000 steps for one revolution...

This means that one revolution of rotary table will take How many seconds to complete?
Regards

[Khalid]

Hi Steve,
by reading the following document of Mariss its confusing... It seems that with different speed the G203V changes microstep..At a specific speed it runs in full step mode while in low speed it runs in microstep.. a difficult archetecture
http://www.geckodrive.com/upload/How...your_motor.pdf