Problem with digital outputs

Kits PC Related Projects
1

Hi,

I’m having trouble with getting an LED to light from the digital outputs. I am connecting positive terminal of the LED to the digital output that I am using and the gnd to the gnd terminal on the board. The light for the corresponding digital output on the board is lighting. I get no reading on a voltmeter for potential difference between the digital output and the ground. How do I get the digital outputs to actually output something?

What is the clamp terminal for on the board?

Also, from the analogue inputs, what sort of sampling rate can I expect from the board? Is 20ms unrealistic?

I bought the board pre-assembled so shouldn’t have any building issues.

Many thanks,

Frokoy

2

Both the digital outputs and PWM outputs are open collector outputs.
These outputs do not output any voltage.
You have to connect the LED in series with a resistor (1k) between the digital output and external voltage source plus (+) pole. Connect the (-) of the external voltage source to the GND of the card.
Please check also: Open collector contacts or outputs, what are these things?

[quote]What is the clamp terminal for on the board?[/quote]The CLAMP is used to protect the output transistors when inductive load is connected to the digital outputs.

Please see the manual p. 19 for more details how to use these terminals.

You may also download this datasheet of the output transistor array to see its internal structure on p. 4:
ca.geocities.com/xxxtoytech/ULN2803D.pdf

[quote]Also, from the analogue inputs, what sort of sampling rate can I expect from the board? Is 20ms unrealistic?[/quote]No, this is not unrealistic. You can get maximum sampling rate of 10ms.

3

Thanks very much. Being a novice though, I’m still a bit stuck.

I want the digital outputs to provide a logic 1 (5V) to an input from another circuit. Is there any way of doing this like connecting 5V between the CLAMP and GND terminals on the board?

Sorry for not getting this,

Frokoy.

4

Yes, connect external +5V to the CLAMP terminal and external voltage minus (-) to GND terminal of the board.
Put a pull-up resistor between the CLAMP and the digital output. Resistor value is not critical, may be 1k or higher.
After doing this, you’ll get about 5V swing from the digital output of the K8055 to the input of the other circuit.

5

Thanks very much! Very clear explanation that I can understand and works.

Now I have everything working. Thank you for your kind and helpful support.