[ynneb]

Hey guys, please dont think that my silence means that I dont look in here daily.

You are all doing a great job. Since I am not that good with electronics I dont have much to add to your conversation. I am just waiting for the go ahead to be given by the technical team here.
Just let me know when you think it is finished.

[tachus42]

Phil I'm seeing the new images but not the new eagle files on your site.
If you where using 6n138s on a breakout board without buffers you could make the threshold adjustable by adjusting the supply voltage on the parallel port side.

Dave I did use 24 thou between ic pins works fine for me but Milelage may vary ...

I have been thinking for a while on how to make a simple discrete bipolar chopper. The chopper is straight forward enough but the H bridge gets complicated real fast when you consider the high side drivers and the 6 needed for a 3 axis setup. It could be a good trade off to use a spit supply with half bridges and possibly a 5 or 10 volt supply
"on top" of the positive rail for the high side drivers - any thoughts?

[pminmo]

http://webpages.charter.net/pminmo/OSuni.brd
http://webpages.charter.net/pminmo/OSuni.sch

do a save as.

[pminmo]

T442 look at the attached eagle file for how to handle the bridge.

Phil

[tachus42]

Phil those links still link to the old versions. Downloaded serveral times and switched to a different proxy, still the same.
By bipolar chopper i meant not unipolar if there was any confusion. The bridge isn't to bad using complementry transistors but try doing it with N Channel Mosfets and laying it out on a smallish single sided board...

[davesaudio]

I think it was mentioned earlier,how about:
ordinary(non logic) mosfets (are beefier) driven by totem pole (pnp npn) pair?
even for unipolar use?
comments?

[pminmo]

Tachus,
I uploaded the files again, downloaded them and they are the new version now for sure. The circuit I sent is a Bipolar chopper. Uses the L297 for sequencing and it analog portion for the chopper. As for running Power FETS, using a charge pump to get the higher gate voltage is an easy solution. I believe Maxim makes one.

Phil

[pminmo]

BTW, I'm going to be offline for 5 days due to travel. no laptop :-(

Phil

[tachus42]

I must have to much time on my hands so I've roughed up a Half bridge Bipolar chopper stepper board. Don't try and build it yet as it's not complete.

Pro's;
Cheap, No Rare parts, Single Sided Board, As much current as you want.

Cons: Lots of bits, Complicted Power Supply, Need MOSFETS with voltage rating twice what the stepper gets.

The power supply will need Positive and Negative rails with the usual 5 volt logic supply plus another Low current supply 5 to 10 volts higher than the positive rail
this could be provided by a voltage multipler from the main transformer or spare winding.

Have a look and see what you think, To complicated, messy? Or something you would tackle if you had the need?

[Greg Fill]

I cannot see what you guys are doing because I do not have Eagle. I use Orcad. Here is a PDF of the discrete bridge drive circuit I am using now on my design. As you see the high side MOSFETS are driven by a simple 3 transistor drive circuit. It is fast, cheap and very reliable. I have used it in many designs over the years. To make this circuit work you need a 12 VDC supply. The low side MOSFETs are driven by a common low side MOSFET driver like the MC3415x, microchip TC442x etc running at 12 volts. The gate drive for the high side MOSFETS is derived from the charge pump circuit consisting Q21 and Q22 and the 12 volt supply. With this circuit Vgs for the high side MOSFETS = Vmotor + 12V. You do not need Logic level FETS because the Vgs is 12 volts. The boost drive needs a simple squarewave signal applied at BOOST. BOOST needs to be from 2 to 20 kHz and is not critical. I use various MOSFETS but the RFD3055, IRF540 and IRF550 are great choices. The IRF540 and IRF550 allow a motor supply of 60 volts, the RFD3055 about 30 volts. In my schematic I show a lot of 1N4148's. You can easily replace these with UF4002's if you are not comfortable with using them.

Because I do not see your schematic I cannot understand why the need for a negative supply. Is it possible for you to output a PDF of what you are planning.

[tachus42]

Ok Greg Pdf file attached.
The need for the negative supply is because the intention is to be a cheapskate with output devices. Not so much for cost but to simplify layout and construction. In your design you are aware that the current in the sense resistor will go negative once the MOSFETS turn off or does the design use a fixed off time?
What i was sugesting with the voltage mutilplier was that if you wanted to keep things really simple you could run it on 50/60 Hz from the power transformer.

[Greg Fill]

Thanks tachus, yes I am aware of the current flow :-). The current direction is not a problem and it depends on the decay mode the bridge is operating in. In a SLOW DECAY mode the sense resistor doesn't even see the current flowing because of the recirculation path. During a FAST DECAY mode the current will reverse direction but again it does not matter because the control is a fixed off time (actually variable but for the discussion it does not matter). I have other prototypes where I used an AC current measurement so I could have a fancier current control but I found that it really was not necessary for what I was trying to do and a "chopper" is fine.

Did I mention the controller is complete and I am using now? All I am trying to do to complete my DIY package is finish the VB software that allows you to program the onboard micro and set its operating characteristics. Stepper type Unipolar/Bipolar, motor current, # of microsteps, % Mixed Mode decay, chopper frequency, etc. are all programmable and changeable at any time.

It is summer here of course and me and the family have to take advantage of the short season we get so presently I do not have much spare time to finish it.

[Greg Fill]

Tachus, after I sent my message I downloaded your PDF. LOL It's uncanny how similar our schematics are. The AC current measurement circuit you used is what I used previously. Except I find the LM324 have to slow a slew rate and I use faster opamps. Your highside drive is the same and your FET choice is the same. I also see you are not afraid to use 4148's. I found that it was easier from a layout and cost point of view to use a MC34152 as the low side driver instead of using discretes. Replace from the 74HC32 to JP2 with a micro and you have my circuit.

[tachus42]

The Moset drive circuit is one I've seen used all over the placeand works well. The I agree the b/w, slew rate of the 324 could be a problem, I wasn't plannig on using much gain in the rectifier.

I assume fast decay mode returns the inductors energy to the power supply and slow mode has either the top or bottom pairs of the bridge turned on. - thats something you can't do with a half bridge.

I modeled the output stage with spice and as you know 4148s are just fine.

[Greg Fill]

Yes for a small signal diode the 1N4148 is a great little workhorse. The LM324 won't be a problem it just may be a little slow. The good part is that the current in the winding changes slowly as well. The MOSFET drive circuit is very common and in the old days this is all we had. There were no half bridge IR2112 driver chips etc.

For the turn OFF portion of the drive circuit which consists of the zener, the resistor, the PNP and the diode connected to the gate, in the distant past I have used a 3 pin device specific for this task. If I remember correctly a MDC1000A from Motorola, but I am not even sure if you can get it anymore. There may be equivalents but I didn't bother to look.

FAST DECAY does return the winding energy to the power supply. SLOW DECAY does recirculate in either the top or bottom pairs.

[slp_prlzys]

Hi,

I realized the pminmo would be gone for a few days,
so I'd ask these to the electronic gurus.

I'm trying to build the controller that uses discrete components
that I got from pminmo webpage, and since the layout has change
from the original design the wiring layout on the docs are not the same.

I built the board with the 7805 installed, I was wondering what voltage
should I use to power the thing, should I use whatever I will be using for
the motors? I tried to power it with a 9 volts adapter and both the LED's
lit up, does it supposed to do that? I was under the impressing that the probe LED would lit only when the test lead is used. I haven't tested it yet with a motor and parallel port connection, 'just want to see if the thing powers up. Any help would be greatly appreciated.

thanks.

for pminmo whenever you'll be back,

I also want to build the 5804 version of your controller,
since I already got the chips for it, but the pcb doesn't
seem to have the place for 7414 that's present on the layout
atleast that's what I thought I'm seeing, and thanks for sharing.

Mhel

[pminmo]

Just got back,
Yes I hadn't updated the docs on the discrete board, looks like I didn't update the copper bitmap. Will get to it in the next 24 hours. Yes the probe LED will light just open air, wired to nothing. Solder a wire in the probe pin and touch the wire to gnd and it should go out if that portion is working properly. If you want the probe led out when the probe wire is touched to nothing solder a 10K resistor from the probe pad to gnd.

[slp_prlzys]

thanks pminmo

the probe seems to be working, the probe LED shuts off
whenever I touch the probe pin to the ground, what about
the voltage requirements though?

I'm testing it using a small Toshiba motor rated at .32A, and have 5 wire leads
I think this is good for testing because of small current requirement,
but I will be using the controller for motor I scavenged from
Laserjet printers and it has 6 wire leads.

Also if I may ask, what program should I be using to test for step
and direction functionality.

Let me know when the 5804 board becomes available,
I'm having fun with my new found knowledge on making pcb
using sensitize pcb and my inkjet printer.

Thanks.

[pminmo]

slp,
I updated the 5804 bitmap and the unipolar document. If the 5804 is installed 8 to 35 volts dc. I gave a little bit of c/o instructions, will add more as time permits and is needed. keep me posted.

Phil

[slp_prlzys]

thanks for the update,

I have to tell you that my knowledge of
electronics is very limited, but I'm learning.

I tried to follow your instruction on probing
(nice new docs btw) since no smoke is coming
out of it I just poke all the pins and here are my findings:

7414

pin#
1 On
2 OFF
3 ON
4 ON
5 OFF
6 On
7 OFF
8 On
9 On
10 On
11 OFF
12 OFF
13 On
14 On


4013

1 OFF
2 On
3 On
4 OFF
5 On
6 OFF
7 OFF
8 OFF
9 On
10 OFF
11 ON
12 OFF
13 OFF
14 On

4030

1 OFF
2 On
3 On
4 OFF
5 OFF
6 OFF
7 OFF
8 On
9 On
10 On
11 OFF
12 On
13 On
14 On

Note that there are some pins that are On that is in normal
state unlike the others that Brights up when probed. The probe
LED is normally On when the power is supplied.

So am I ready to hook my motor now?
Just eager to have a spinning motor