I am new to Arduino. I have figured out the programming to drive a pin to a high voltage to make a fast square wave of about 200 microseconds.
What I want to do is use that pin to control a TTL device. I want to be careful and want to avoid burning up the TTL device with too high of voltage or current from the Arduino. Does anyone have advice on this?
I looked up the general description of a TTL device and it says that it can take an input of 2 V to 5 V for a “HIGH” with a current of 40 uA.
The TTL “LOW” input is described as 0 V to 0.8 V and current of 1.6 mA.
How do I take the HIGH and LOW ouput of the pin of the Arduino and connect it to my TTL device without damaging the TTL device with too much voltage or current from the Arduino?
I am thinking I need to put a resistor (~10k-ish) between the Arduino output pin and ground. But I don’t know what value is best. Then to prevent current from going into the TTL device, I am thinking of putting a much large resistor (~1 Mega-Ohm) and connecting it from the Arduino output pin to the TTL device’s input.
Does this sound good or not? Will it make the Arduino output behave like a TTL input for the TTL device?
I don’t know if this matters, but the Arduino is powered by a USB connection.