I wish to run a small bipolar stepper motor from my K8055. Can I use a 5v clamp arrangement to drive a L293 hbridge by hooking up digital output 1-4 to the corresponding 1-4 pins on chip. I have already written a programe which cycles through the digital outputs with a small delay interval between each switch sequence. I would be grateful for circuit diagram if anyone has all ready done this.
Thanks in anticpation 
[quote]Can I use a 5v clamp arrangement to drive a L293 hbridge by hooking up digital output 1-4 to the corresponding 1-4 pins on chip.[/quote]According to the datasheet of the L293, all the inputs are TTL compatible.
pobot.org/IMG/pdf/l293.pdf
This means that you may connect the K8055 digital outputs to the L293 inputs without using pull-up resistors.
It may be anyhow a good idea to ensure the digital high state by using 10k pull-up resistors between the L293 inputs and VCC1 terminal.
More about the pull-up resistors please see:
viewtopic.php?f=12&t=6032
viewtopic.php?f=3&t=5028
viewtopic.php?f=3&t=4224
Thanks for your advice, I have modified my circuit including the 10k pull up resistors as per your advice,but unfortunately I not got any further.
I have measured the following data:
clamp to GND = 4.6v
By switching the individual digital outputs, I got the following data (V) without the stepper motor:
D D Input Output
1 0.61 0.61 0.11
2 0.63 0.63 0.10
3 0.62 0.62 0.11
4 0.64 0.64 4.60
I then disconnected the inputs and applied a connectionfrom my external supply to each of the inputs in turn. In the case of 1-3 the outputs were switched. In the case of 4, it remained switch all the time. I guess that I have fried this output???
My question is should I be getting 4.6v on D1-4 when each is swithed?
I shall obviously need to order a new chip, is the L the best one or is there a better alternative. I would like to use this in the future to swicth individual items such as relays, etc.
Thanks in anticipation.
This diagram shows how to use the open collector outputs to connect different devices there:
If you have a LED you may connect it with a series resistor between the external power supply and digital output of the card. It should show if the card output is still working.
You can connect a relay directly to the K8055 if the relay coil current is less than 100mA.
When you connect a relay or any other inductive component to the output, it must be connected between the digital output and CLAMP terminal.
I have connected an LED and 1K resistor as shown in the diagram above, however when the digital output 1-4 are switched, I still do not get a voltage of more than 0.62V on the L293 in pins and so the chip does not switch. I have got a schematic diagram of my circuit but I have no access to a public server. If you send an email to david_small@btinternet.com, I could email it as an attachment. I am new to electronics and do not fully understand terms like pull up resistors etc. When I purchased the board, I thought all I would have do was connect relays, chips, etc to link the units together. I am keen to learn.
Thank you for your assistance so far.
[quote]I still do not get a voltage of more than 0.62V on the L293 in pins and so the chip does not switch. [/quote]Do the output pins of the K8055 give full voltage swing (0.64V to 4.60V) if you disconnect them from the L293 inputs?
Keep the external (pull-up) resistors between the K8055 outputs and power supply +pole connected when testing the K8055 outputs.
The outputs of the K8055 are open collector outputs and there is no voltage swing available if there are no resistors between the output pins and the power supply +pole. The purpose of these resistors is to “pull up” the K8055 outputs.
The K8055 outputs are “active low”. This means that when the output is “ON”, it is pulled down. The LED indicator of this output is lit in this case.
Thank you for your advice, I have added the resistors and everything is working satisfactorily.
