[Arduino rf communication]

I want to make 2x arduino talk to each other via rf and using sensors. If 1x arduino detects an obstacle it sends a signal to another arduino to lyt a red lyt, if the first arduino area is clear it sends a signal to the 2x arduino to switch the red lyt to green.

This is to be used in a railway station, were arduino 1 is in the station arduino 2 is on the approach to the station, if 1 has a train then 2 is red, if no train in 1 area then 2 can proceed to station.

I hope that is understandable to you. 

Plz try to help. 

[email protected] 

[Lm3914 lead acid car battery monitor]

I need to make a car battery monitor using the LM3914 ic.

led 1 = 10v, led 10 = 13.8v

what value resistors do I need?

i have a full stock of resistor values, 2x LM3914'S and 2x 10 led bar graph displays, but cant experiment and blow an IC.

I also have a good range of capacitors, diodes etc. 

[battery level indicator]

On 7/27/2018 at 3:51 PM, audioguru said:

The LM3914 in a DIP case is not made anymore. Buy them before they are all gone.

I need to have led 10 at 13.8v led 1 at 10.0v what resistor values will I need?