Promise

[B.v.d.Holst]

Hi people,
Iám a new-comer on this site ( about 1 year ?)and a boring about people how REPLY to you and PROMISE to help and give than no answe more, I sink this is not the purpose off the forum .Well so wy see into the Nederlands make no promuse if you will make it real,if not don't interfere .I dont my english is bad bud I try it.

[gar]

051226-1001 EST USA

B.v.d.Holst:

Reading your current post and your other posts I believe your current post says the following:

I have been viewing this forum for about 1 year.

(You have submitted about 4 post with very few responses.)
(I think your word boring maybe should be problem.)

I have a problem with the replies that I have received. If someone replies and promises to provide a response, then they should follow through with the promised response, or they should never interfere in the first place.

(Apparently in one of your requests for a schematic you received one response. Then you asked for a direct mail response. Did you ever get that mail response and is the problem that you did not get a response when you thought it was promised?)

--------------

Some comments that may or may not help you. I do not know your background so maybe what follows won't be of any value.

I used Google to search for SLA7026 and then went to the site with the Google title "SLA7026.PDF,SANKEN 2-Phase Stepper Motor Unipolar Driver ICs ,alldatasheet,". This takes you to an address starting with www.alldatasheet.com ....... . Here there is information on the basic circuit.

This driver requires that you provide four inputs from some source to control the sequencing of the individual coil drivers. As I view this device it is four relatively independent pulse width modulated current limited drivers, but each pair (2) shares a common current sense resistor. Also in the internal logic there is cross coupling that prevents both drivers in the same pair from being on at the same time. If two inputs of one driver pair are both high, then both driver outputs are inhibited.

Note on the schematic shown there appears to be an external peak voltage limiter from Vcc to common. This is important to limit voltage during rapid deceleration.

I have never worked with this device so take my information as something to help you do your own analysis of the operation of the device.

.

[gar]

060101-0730 EST USA

I have had some PM communication with B.v.d.Holst (Bob). He needs help from someone in his country and close to him.

I believe his original questions were really how to build a circuit to take an UP/DOWN direction signal and a STEP pulse signal and generate the the signals INa, IN/a, INb, and IN/b required at the input to the SLA7026.

Here was my suggestion to Bob:

"First you need a two stage up-down counter. This will have the four possible binary outputs of

00
01
10
11

If these counter outputs are fed to the inputs of a ROM and you program the ROM for the SLA7026 truth table then you have a simple circuit.

A different way uses combinatorial logic to map the counter outputs to the desired inputs to the SLA7026.

From the truth table in the SLA7026 data sheet we have the following mapping

Input Output to SLA

00 --- 1010
01 --- 0110
10 --- 0101
11 --- 1001

The output of a firsrt exclusive OR (XOR, for example 74LS86) from the counter outputs produces the second from left output column. This would go to pin 5 (IN/a). The complement (NOT, inverted) of the first exclusive OR goes to pin 6 (INa).

Use a second XOR to generate the right most output column pin 16 (IN/b). The inputs to this second XOR are: the output of the first XOR, and the right column of the counter outputs. Then the next to right most output column is the complement of the right most column and goes to pin 17 (INb).

Draw this out and make sure that my logic is correct.

Also note you can use an XOR as an inverter by making one input a 1 or high.

If my count is correct one 74LS86 package (has 4 XORs) will do this mapping for you."

........

"Make sure you double check my logic. Also there are differences in the way different up-down counters are clocked."

Bob has had a motorcycle accident and so has not had a chance to work with this information. But I sense he needs local help.

More specifically some pinouts follow, but I would like some others to check my logic, and maybe check out and draw the circuit for Bob.

Consider a 74LS191 up/down counter and use only the A and B outputs. Pin 16 is Vcc, pin 8 is common, pin 5 is UP/DOWN, pin 14 clock, pin 3 is A output and pin 2 is B out.

On the 74LS86 connect pins 1 and 13 to pin 2 (B out) of the LS191, and pin 12 to pin 3 of LS191 (A out).

On the LS86 connect pin 11 to 10 and 2 and also to pin 5 (IN/a) of SLA7026.

LS86 pins 5 and 9 to Vcc.

LS86 pin 3 to 4 and also to pin 16 (IN/b) of SLA7026.

LS86 pin 8 to pin 6 (INa) of SLA7026, and pin 6 to pin 17 (INb) of SLA7026.

The above logic provides full step operation of the steppers.

Are there any errors in my logic?

.

[Al_The_Man]

I am no expert on stepper circuits, but I believe there are many stepper motor translator/drivers out there by Allegro and others, the descrete logic may be the way to go if these IC's are not available in various parts of the world.
A web search for stepper translators should bring in a few, or the forums here I am sure have covered some of these ics.
Al.

[pminmo]

The problem with the SLA7024 is you need to invest more into the logic around it than the part is worth. I mean you could design a stepper driver with vacuum tubes, but why?
If you had to use it, a cheap micro controller like an AVR or PIC is probably makes the most sense.

Phil

[AbSat]

Just for a test I put a SLA7024 behind a L297 and used the chopper in the SLA.
It works ok, but I am not shure of the chopper. The chopper frequentie is very dependend on the current, so I will try the chopper in the L297 also and look what the best solution is.
I already maild the schematics to Bob.
I have a number of SLA drivers laying around so thats why I did the test.
When halfstep is enough why not use them.

AbSat.