Thread: How do I construct these circuits

1. How do I construct these circuits

How do I construct these circuits, which resistors, transistors do I need?

Thank You
William

2. William,

That depends on what your control signal voltage is. With the exception of the 7406 (inverting buffer) which accepts 5V TTL logic.

You could most likely use just about any general purpose NPN switching transistor like a 2N3904 for instance. Resistor selection will depend on your control voltage.

Steve

3. I assume input voltage is +5 volts since it's coming off printer port. So which resistor do I need? (sorry I'm not electrical engineer)

Regards
William

4. Download PSpice and design away, it knows electronics for you. http://www.engr.uky.edu/~cathey/pspice061301.html

5. Ok,
Use a General purpose NPN transistor 2N3904 or 2N2222 or equivilant.
The resistor that goes from the control signal (printer port) to the base of the transistor should be 4.7 K ohms. The resistor from the base of the transistor to the control logic common (printer port ground) should be 10 K ohms.
Be carefull not to over heat the transistor when soldering it in. You can wrap a piece of wet paper towel around it while soldering to keep it cool. just make sure to dry it before applying power.

Steve

6. Chances are you only need this type of circuit if your signal is weak or not a pure square wave. The inputs are generally opto-isolated so you provide 5v and common from your external source where the signal is generated from. If the square shaped signal is not compromised, you do not gain anything by adding more to the circuit.

Here is another way to reform, square or cleaning the inputs with an IC that doesn't invert the signal or take discrete components like transistors or resistors, with the bonus in that there are six on each device. Other versions may have 8. If you need inverting and squaring, use one that states it like a 7414 and the like.

Non-inverting TTL schmitt trigger

DC

7. Originally Posted by FeldWill

How do I construct these circuits, which resistors, transistors do I need?

Thank You
William
If you are using a PC to drive it, the circuit is basically already in the LPT port....You need 5V from the PC side to the opto, then a 560 resistor to the LPT port pin, usually pins 2 through 9. The 5V on the PC side also needs it's common to the PC LPT port pins 18 through 25.

8. Originally Posted by pminmo
If you are using a PC to drive it, the circuit is basically already in the LPT port....You need 5V from the PC side to the opto, then a 560 resistor to the LPT port pin, usually pins 2 through 9. The 5V on the PC side also needs it's common to the PC LPT port pins 18 through 25.
If the output of the parallel port were 12v, then I could see the need for a 560 ohm voltage dropping resistor. Since the inputs for the opto-coupler are 4.5 - 6v the resistors wouldn't be needed with a 5v LPT output would they?

The other things I'll add, is that some of the newer LPT ports and more common on laptops may only output 3.3v for LPT signals. There may be a need to pump them anyways. That would be another good reason for using the buffer/line driver as I posted earlier.

DC

9. Originally Posted by One of Many
If the output of the parallel port were 12v, then I could see the need for a 560 ohm voltage dropping resistor. Since the inputs for the opto-coupler are 4.5 - 6v the resistors wouldn't be needed with a 5v LPT output would they?

The other things I'll add, is that some of the newer LPT ports and more common on laptops may only output 3.3v for LPT signals. There may be a need to pump them anyways. That would be another good reason for using the buffer/line driver as I posted earlier.

DC
If using a 5V supply you need some current limiting method to protect the opto as well as the LPT port driver. Since it would be using the "LO" (sink) side of the driver then the only concern of the 3.3V output would be if it's high enough for the opto to turn off. On being 5V supply to opto thru resistor to LO output of the LPT port. Assuming a 2V opto, and a .7V "LO" the resistor should be more in the 150 ohm region for 16ma. The 3.3V on LPT ports is a "loaded" HI state usually. i.e. trying to drive a load while "HI". Although the 1284 spec allows for a loaded HI to actually go into the mid 2V region and still be in spec. If the LPT port is only outputting 3.3V and the opto isn't turning OFF, then a diode inline with the 5V is a simple solution.
As to laptop verses desktop, they both conform to the 1284 Spec. Some laptops will when running on battery will produce a lower voltage, but I wonder how many users would run a machine from a laptop on a battery.......

10. Dear FeldWill,

You said...

I assume input voltage is +5 volts since it's coming off printer port.

It would be a very good idea to check what it actually is IMVVHO, before going further.

Best wishes,
Martin

11. Originally Posted by FeldWill

How do I construct these circuits, which resistors, transistors do I need?

Thank You
William
William,

Your .pdf file is from one of the drive manuals from Superior Electric SLO_SYN models SS2000-MD7 or the -MD4 manual.

If you are using these drives, these circuits are integrated into the drive inputs themselves and can be driven by normal TTL level signals.

If you need to wire up these drives, there is info on this site on all the proper connections, which I presented about two years ago. Do a search for SS2000-MD7 or MD4 drives. The wiring is the same for both. There are just more options on the MD7 drive. The 4 and 7 indicate the current the drive can handle safely.

If you just want to build the interfaces, for signal conversion, just learn the difference between a NPN and a PNP transistor and wire accordingly. As for 5 VDC logic, just use Schmitt trigger IC's.

Jerry

12. If your wanting to connect the drives to a PC LPT port see below.