Description (From Recipaedia)
An electric photodiode. Used to detect light. The diode will set the state of an electric circuit to 1 if there is enough light hitting its surface. It has outputs on all sides for easy connection and can be placed on any horizontal or vertical surface.
Crafting
Use 3 copper ingots and one glass to craft photodiode. You get 2 diodes.
Hooking it Up
Simply place the diode where you wish and run a single wire from any side or back of the diode. Feed that wire to the rest of your circuit.
Lighting values
The photoelectric diode reacts to the level of light around it and is mostly used to detect environmental light from the sun and moon. The lighting values for various times of day are as listed below. These levels were measured under a clear, open sky without nearby structures blocking the sensor.
- Full Day – 1.5V (F)
- Dusk – 1.1V (B)
- Sunset – 0.9V
- Dark – 0.7V
- Night – 0.5V
- Midnight (new moon) – 0.0V
- Dawn – 1.1 to 1.3V (B to D)
The dawn and dusk levels are lower when it’s a new moon that’s setting or rising.
All this means that if you use the diode to turn lights on at dark, you should not use the simple NOT gate. Since version 1.29, the lightbulb takes analog input signals and will not turn fully on, except on the darkest of nights. The lightbulb page has a circuit that may be used as an interface or controller, to allow it to be on full once the light gets below a certain level. You can use the values listed below to program the controller when to turn the lights on fully. The string used to program the memory bank is included to make it easier.
- If you want the lights to come on only once it’s dark, turn them on below 0.7V : FFFFFFF000000000
- To turn them on at dusk, set it to under 0.8V: FFFFFFFF00000000
- To turn them on when it starts to get dark, set it to under 1.2V: FFFFFFFFFFFF0000
- You can also have the lights turn on gradually as it gets darker so they come on as the light first diminishes and are fully on once it’s completely dark. Use: FFFFFFFEDCBA9800
If your diode must be placed where it’s a little darker than in the open, you just insert another ‘F’ at the beginning of the line. This will make the light come on when it’s a little brighter. If there’s a bit of artificial light on the sensor, delete an ‘F’ from the beginning of the line and this will make them stay off until it’s a little darker. Just remember the sensor still must be isolated from the light of whatever it’s controlling, or it may go into feedback and oscillate on/off/on/off…
See the lightbulb page for the simple controller circuit and the memory bank page for programming the bank.
Adventure map uses
- You may have a falling wall that opens up an area. It may be difficult to detect when this wall is triggered. If the character side of the wall is lighted, you could place a photodiode on the dark side of the wall and it will trigger once the wall is gone.
- If you have a long hallway, you could have the lights come on in sequence for effect. The first light comes on from a switch or other trigger. The next light is triggered by a photodiode that sees the light from the first light and turns the next group on. And so on. This setup doesn’t use the NOT type circuit. Instead it is directly connected to the lights, or through a ‘controller circuit’ that does not invert the signal. This type of circuit is not susceptible to the oscillating feedback. Instead, if there is feedback, the lights won’t turn off due to the sensor.
- Another use in adventure maps is setting photodiodes next to major explosives, so if light floods from player breaking it or otherwise, the explosive fuse is lit.