Again, your schematic is not at all clear.· Please draw it as you've wired it including the stepper coil and the LED and transistor.· There's a Nuts and Volts Column (I think it's #6) that covers the use of transistors with a Stamp to control LEDs, relays, motor coils, etc.· The Industrial Control Tutorial also covers this topic.· Both include sample circuit diagrams and sample Stamp code.· Go to the main Parallax webpage, click on the Resources tab.· You'll see "Nuts and Volts Columns" which you can click on and you'll see "Downloads".· When you click on that, you'll see "Stamps in Class Downloads".· The tutorials are there.
I tried those links and they helped me a bit but there wasn't much there that came near to solving my problem.
However I do·have a question about the stepper
When I connect the common wire of my stepper to the + 14.4V supply voltage, do the coils receive power right away???
Common sense dictates that they do, but then how do I control which one is turned on when they are already on???
This seems like a really (for a lack of a better word)·ignorant question, but with my current knowledge I am not able to comprehend it at the moment.
Now, proceed to identify individual coils in order of sequence.
Connect the common lead to the positive of your battery or power supply.
Connect any one of the other four leads to ground. This will be Coil 4.
With Coil 4 still grounded, connect another lead to ground. If the shaft does not move, you have Coil 2. If the shaft jogs clockwise, you have Coil 3. If the shaft jobs counter-clockwise, you have Coil 1.
Repeat until you have identified all four coils.
However this operation to identify coils (even though I know them) doesn't work because the stepper doesnt move at all no matter what 2 coils are connected to the - terminal of my power supply?· Does this mean I need a higher battery source.· My current battery source is two 7.2 batteries wired in series to produce 14.4 volts at 2000mAh.· Or is my stepper inoperable?
Your stepper might be inoperative. Your batteries might be drained. Do you have a multimeter? That would answer some of those questions. RadioShack has them from $10 up. They can measure voltage and resistance at the very least.
To conduct electricity, there have to be two wires or two connections, one where the electrons go in (-) and one where the electrons come out (+). If you connect the stepper's common lead to the (+) battery terminal, no current will flow. When you also connect another lead to the (-) battery terminal, current will flow through the coil connected between that lead and the common terminal. If you also connect another lead to the (-) battery terminal, current will also flow through the coil connected between that lead and the common terminal. If there's a transistor switch in one lead and the transistor is off, it's just as if the lead wasn't connected (up to the voltage limits of the transistor ... it breaks down above that voltage and will probably melt somewhere). If the transistor is on, it's just as if the lead was connected directly (up to the current limits of the transistor ... some part of it will probably melt above that current).
Mike Green said...
Your stepper might be inoperative. Your batteries might be drained. Do you have a multimeter? That would answer some of those questions. RadioShack has them from $10 up. They can measure voltage and resistance at the very least.
To conduct electricity, there have to be two wires or two connections, one where the electrons go in (-) and one where the electrons come out (+). If you connect the stepper's common lead to the (+) battery terminal, no current will flow. When you also connect another lead to the (-) battery terminal, current will flow through the coil connected between that lead and the common terminal. If you also connect another lead to the (-) battery terminal, current will also flow through the coil connected between that lead and the common terminal. If there's a transistor switch in one lead and the transistor is off, it's just as if the lead wasn't connected (up to the voltage limits of the transistor ... it breaks down above that voltage and will probably melt somewhere). If the transistor is on, it's just as if the lead was connected directly (up to the current limits of the transistor ... some part of it will probably melt above that current).
Thanks Mike,
The stepper motor moved!!!! · My circuit was right from the beginning however I had one small problem.·
Now, proceed to identify individual coils in order of sequence.
Connect the common lead to the positive of your battery or power supply.
Connect any one of the other four leads to ground. This will be Coil 4.
With Coil 4 still grounded, connect another lead to ground. If the shaft does not move, you have Coil 2. If the shaft jogs clockwise, you have Coil 3. If the shaft jobs counter-clockwise, you have Coil 1.
Repeat until you have identified all four coils.
At first I believed that this procdedure above did not work.· However my motor had such a TINY step angle of 0.1 degrees (or lower) that I did not detect it moving at all.· Only when I rewired the motor and observed it carefully it started to move.· My other problem was my code,· however I found some great sample codes online and configured them to my needs.
Once again, thanks to all that helped, I really appreciate.
Technic-R-C
P.S.· Knowing me, I will probably be back with another question later.
In regard to the TIP31, in the datasheet it states that the maximum current value going into the base wire of the transistor is 1 Amp.
How many mA does the stamp output per 1 transistor base??
I would like to run 3 steppers, how many transistors can I have turned on high at once? (6 would be great)
You're still asking questions that imply that you don't understand the jargon or basic concepts
1) Maximum values on a datasheet, particularly absolute maximum values usually refer to values above which damage will occur. A maximum base current is the value above which the on-chip wiring for the base will melt.
2) The BS2 is built with a PIC 16F57 processor chip. Microchip puts out a datasheet for this. The maximum source current from an I/O pin (logic high) is 20mA. Above this may damage the chip. There are also 8-pin group limits (50mA) and total chip current limits (100mA) beyond which the chip may become damaged. You may notice that, in the schematics showing this sort of use, there's always a resistor in series with the base lead. This is to limit the current into the base of the transistor and out of the I/O pin of the Stamp. This resistor would be 220 Ohms if you wanted 20mA of source current, 330 Ohms for roughly 15mA or 470 Ohms for roughly 10mA. The TIP31 has a current gain (Hfe) of roughly 25, so 25 x 20mA = 500mA. If you need more collector current, you'll need a transistor with more gain, possibly a Darlington pair like the TIP120 with a gain of 1000. The base current would be lower because of the higher base-emitter voltage, but the higher gain would compensate.
Comments
However I do·have a question about the stepper
When I connect the common wire of my stepper to the + 14.4V supply voltage, do the coils receive power right away???
Common sense dictates that they do, but then how do I control which one is turned on when they are already on???
This seems like a really (for a lack of a better word)·ignorant question, but with my current knowledge I am not able to comprehend it at the moment.
Technic-R-C
Is it that you have the test LEDs and resistors still in circuit, in parallel with the coils?·
If so, remove them.
That solved the problem of the LED's.· But this means that the coils are always on and I don't have contol over them.... confusing...
I came upon a·quote in a stepper control website
However this operation to identify coils (even though I know them) doesn't work because the stepper doesnt move at all no matter what 2 coils are connected to the - terminal of my power supply?· Does this mean I need a higher battery source.· My current battery source is two 7.2 batteries wired in series to produce 14.4 volts at 2000mAh.· Or is my stepper inoperable?
Technic-R-C
To conduct electricity, there have to be two wires or two connections, one where the electrons go in (-) and one where the electrons come out (+). If you connect the stepper's common lead to the (+) battery terminal, no current will flow. When you also connect another lead to the (-) battery terminal, current will flow through the coil connected between that lead and the common terminal. If you also connect another lead to the (-) battery terminal, current will also flow through the coil connected between that lead and the common terminal. If there's a transistor switch in one lead and the transistor is off, it's just as if the lead wasn't connected (up to the voltage limits of the transistor ... it breaks down above that voltage and will probably melt somewhere). If the transistor is on, it's just as if the lead was connected directly (up to the current limits of the transistor ... some part of it will probably melt above that current).
The stepper motor moved!!!!
At first I believed that this procdedure above did not work.· However my motor had such a TINY step angle of 0.1 degrees (or lower) that I did not detect it moving at all.· Only when I rewired the motor and observed it carefully it started to move.· My other problem was my code,· however I found some great sample codes online and configured them to my needs.
Once again, thanks to all that helped, I really appreciate.
Technic-R-C
P.S.· Knowing me, I will probably be back with another question later.
How many mA does the stamp output per 1 transistor base??
I would like to run 3 steppers, how many transistors can I have turned on high at once? (6 would be great)
Technic-R-C
Technic-R-C
1) Maximum values on a datasheet, particularly absolute maximum values usually refer to values above which damage will occur. A maximum base current is the value above which the on-chip wiring for the base will melt.
2) The BS2 is built with a PIC 16F57 processor chip. Microchip puts out a datasheet for this. The maximum source current from an I/O pin (logic high) is 20mA. Above this may damage the chip. There are also 8-pin group limits (50mA) and total chip current limits (100mA) beyond which the chip may become damaged. You may notice that, in the schematics showing this sort of use, there's always a resistor in series with the base lead. This is to limit the current into the base of the transistor and out of the I/O pin of the Stamp. This resistor would be 220 Ohms if you wanted 20mA of source current, 330 Ohms for roughly 15mA or 470 Ohms for roughly 10mA. The TIP31 has a current gain (Hfe) of roughly 25, so 25 x 20mA = 500mA. If you need more collector current, you'll need a transistor with more gain, possibly a Darlington pair like the TIP120 with a gain of 1000. The base current would be lower because of the higher base-emitter voltage, but the higher gain would compensate.
Post Edited (MoMeD) : 8/3/2008 9:47:45 AM GMT
·http://forums.parallax.com/showthread.php?p=641371