Electronic – Circuit to keep two LEDs on when buttons are released

While @JimDearden's answer provides a suitable approach for operating the two infrared LEDs in parallel as desired, my answer addresses the specific question asked, to resolve some possible misunderstandings that may have motivated the question:

• An AND gate is used for taking two or more inputs, and providing a single output representing the logic AND operation on those inputs. The purpose underlying the question is the opposite: To take a single input (from the Arduino pin) and drive two outputs. Hence, no rationale for using an AND gate

• The classic 7400 series TTL logic gates have recommended operating conditions of merely 16 to 22 mA per output (current sink) depending on manufacturer. See the 7408 AND gate for instance. In other words,

  1. They will not sink enough current for two IR LEDs if the output is used as a low-side switch, with the LED between output and the (presumably) 5 Volt supply. (actually they will sink up to 55 mA in short-circuit, but that is beyond recommended safe operating area)
  2. Many 74 series gates will not provide a high side output of any significance for turning on LEDs connected between output and ground - they are designed to be used with a pull-up resistor on the output pin.

  _{Note that some variants of the classic 74 series logic parts can both sink and source current, and there are even some that can deliver outputs in the ampere range. For instance, the 74595 shift register has an equivalent, the TPIC6595, which sinks 1.5 Amperes pulsed current per pin.}

• If the intention is to operate LEDs from the output of a 74 series gate, this won't work the way the output of the Arduino works: The LEDs would have to be connected on the Vcc side, with cathode at the logic gate output, and the output logic will need to be inverted in code.

So, in short, the 7408 AND gate is neither a viable nor a justifiable approach to solving the problem.

The problem here is there is no input to the NOR gates when the switch is open.

Basically, when you have an undriven logic input, the input is undefined. This means it could be high, it could be low, it could toggle randomly as a function of local electrical fields. This is colloquially called a floating input, because the voltage on the input "floats" around as a function of local electromagnetic influences.

Since it seems like you want the inputs to be high except when the switch is closed, you need to add a resistor between the inputs and the positive rail, to pull the inputs into a known state when the switch is open. A few KΩ should be fine.

Ok, more troubleshooting. First, I'd stick pull-ups in there anyways. Relying on the internal behaviour of the input buffer makes me uncomfortable.

Next, rather then just wondering if your solder joints are bad, just measure them! You should see ~Vcc at the input from the switch when the switch is open, and ~Gnd when it's closed. This should be quite easy to test, even with a cheap multimeter.