[Konstantin]

Well the BC546B
Digikey #BC546BOS-ND pricing 1 to 9 $0.28 and 10 to 99 $0.16400
only one choice in Digikey, in Newark we have 3 choices
Newark #20H1736 pricing 1 to 24 $0.063 and 25 to 99 $0.057
Newark #20C0548 pricing 1 to 24 $0.176 and 25 to 99 $0.160
Newark #38C6981 pricing 1 to 24 $0.232 and 25 to 99 $0.182
25 transistors will cost : $1.43 (#20H1736) vs $4.55 (38C6981) vs $4.10 (#BC546BOS-ND)

I wonder if it pays to spend the extra money on more expensive parts?
Or the performance is the same and the only difference is the price.

I am on a budget. And even if I would not be, I would still look for a better price.

Konstantin

[tachus42]

The transistors are not critical, most small signal transistors in a to-92 should be ok.Just check the pinout on the datasheet. For the NPN BC546,547,548,549 A,B or C will all work. Like wise for the PNP 556,557,558,559 are ok. NPN 2n3904 PNP 2n3906 would be another choice.

Konstantin just use the cheapest one. The 20H1736 is ok.

Oh and i don't think the power rating of the Zener was specified on the schematic. It should be 1 Watt.

[Konstantin]

Would anyone explain about the resistors that would limit the current in the chopper board. PDF has this table.
R----Amp
1---1.1
0.82--1.5
0.68--1.7
0.47--2.5
0.33--3.5
0.22--5
0.1---10

I should accomplish that resistance 'R' value to get the ampers I need for my motors, right? What is the wattage for those resistors, any special thing about those resistors?


As for the 'Approximate timing' set by the C1,C3,C5. How should I choose my capacitor? Depending on my motor inductance?


The "R5+R4 (Supply-10)/0.05" value must be in Ohm or kOhm ? It does not matter how many resistors I serie in (R4+R5) it must give me the (Supply-10)/0.05 value, right? So if PSU is 25v then (25-10)/0.05=300 Ohm?
Wattage on those resistors?


Anything special on the JP1?



Konstantin

[tachus42]

Konstantin

If you look back in this thread to the last zip file i posted there is a txt file with the current limit resistor combinations. Yes 300 Ohms is right for the supply droppers use two 150 Ohm in series 1 Watt. Use 3n3 for the timing cap. JP1 wires to the 10 pin header on the driver board to break out the limit switch connections. You don't need to fit those parts if you don't need them.

[pminmo]

Tach if you want to send me some info I'll put a doc together for it, and put it on the website.

Phil

[Konstantin]

Chopper board

Resistor Combinations
Current is total ie both phases added together
1 Watt unless specified


Current--Ideal R--Close Combination
0.25---4.4-----1 x 6.8, 1 x 12
0.5----2.2-----1 x 2.2
0.75---1.47----1 x 2.7, 1 x 3.3
1.0----1.1-----2 x 2.2
1.25---0.88----1 x 1.5, 1 x 2.2
1.5----0.73----3 x 2.2
1.75---0.63----2 x 2.2, 2 x 2.7
2.0----0.55----4 x 2.2
2.5----0.44----2 x 1.5, 2 x 2.2
3.0----0.37----2 x 1.2, 2 x 1.8
3.5----0.31----4 x 1.2
4.0----0.28----2 x 1, 2 x 1.2
5.0----0.22----4 x 1, 1 x 1.8 or 1 x 0.22(5 Watt)
6.0----0.18----1 x 1, 1 x 0.22(5 Watt)
7.0----0.16----1 x 1, 1 x 1.2, 1 x 0.22(5 Watt)
8.0----0.14----3 x 1.2, 1 x 0.22(5 Watt)
9.0----0.12----4 x 1.2, 1 x 2.7, 1 x 0.22(5 Watt)
10.0---0.11----2 x 0.22 (5 Watt)

So my motor is 1.4A/phase, would it be allright to use this settings?
3.0----0.37----2 x 1.2, 2 x 1.8


Konstantin

[tachus42]

Konstantin You got it right.

[tachus42]

Phil what extra info for the chopper board would you like?

I'm about 60% percent done on a 1/4 stepping bipolar chopper. It will be a while before I can get a prototype together and test it unfortunantly. It will be a 4 board set for 3 axises, 3 output boards and a "phase generator" board. The phase generator would be a good place to have a micro but I have come up with a simple discreet logic circuit for it.

[pminmo]

I just probably need all the latest files, not sure which is what.

Phil

[Konstantin]

How about making this open source cnc drivers in a factory?

Once I used to be a reader of another open source project, the OpenEEG or ModularEEG, it was about an electro encephalo graph device 2 to 6 channels. They joined up and talked out with this company in Bulgaria Olimex and made the boards. I have purchased my set of boards and made my own EEG device.
One could take the hardest to build open source cnc board (3 0r 4 axis maybe) and maybe make a deal with Olimex. I guess there has to be a sufficient amount of people that will purchase the drivers, for Olimex to accept making them, I dont really know. But I know that Olimex was the cheapest company that manufactured the ModularEEG boards and with very good quality.
Maybe something similar could be made in this community.


Konstantin.

[pminmo]

I had already contacted olimex, they expressed no interest. They did in fact build my 3977 boards for me. If there was interest I might be willing to buy a quatity of boards and resell them. Not really interesed in making it a commercial venture, just recoup my investment.

Phil

[Konstantin]

I had already contacted olimex, they expressed no interest. They did in fact build my 3977 boards for me. If there was interest I might be willing to buy a quatity of boards and resell them. Not really interesed in making it a commercial venture, just recoup my investment.

Phil

Did Olimex manufactured bare boards for you, or assembld and tested?

Konstantin

[pminmo]

Bare boards. Pretty good quality for the price. The're on vacation this month (August) I have a new board to send them.

Phil

[kd6oji]

OK.. Got my single channel discrete boards made. Got a BOB constructed as well.
I checked the boards as detailed in the directions. Most items seem fine, except I cannot step the motor with it. I tried using a switch to manualy inject pulses, and connecting the STEP line to GROUND. the motor wiggles a little the first few pulses, but it stops and does not step at all. I checked the outputs of IC8, pin 1 is staying low with no IRF44 placed, it should step I think, pin 2 pulses with each switch transition, switch on, pin 2 high, sw off, pin2 low.

I have swapped chips so I don't think thats the problem. and none of the IRF44's are placed so its not a problem there. also checked for grounded pins, nothing evident.. help!!!

[tachus42]

By STEP line do you mean the test point labeled step or the p5 test point?
pin 1 should always be the oppersite to pin 2. You wil get uncertin results trying to manualy pulse the input as switch bounce will give you a random number of input pulses.

[kd6oji]

Pin 1 is always low. Pin 2 switches states responding to the switch.

[Konstantin]

motor hooked up correctly?


Konstantin

[kd6oji]

found the problem..
Boards are not very well done (my bad) have several leaks on the between pin lines in the IC area.
I have a 3 axis that I am going to populate rather than work on these for now, it turned out great. guess thats what I get for using an OLD photo board the resist must have been bad.

[tachus42]

It's always something simple. Its just finding it thats the problem.

[kd6oji]

between JP1-5 and ground.
Looked the other boards over, they have same problems with bad traces between some IC pins.. I need to rework them before they will work properly. Learning a lot though.

Now.. where do the home switches go on the 3 axis?? hrmmm... I will figure it out..