What types of LEDs

[HitMan]

Hi there I have this circuit board for a dishwasher this particular board lets the main board know when the liquid rinse agent is LOW how would I know what the equal replacement LED would be one is black and other white in colour.
Please see attached pictures must appreciate the help

 

[AnalogKid]

My GUESS is that this is a reflective sensor. The clear part is an infrared LED emitter, and the "black" part is an IR-sensitive photo-transistor or photodiode. There are way too many different parts in these packages to guess at a specific part number.

A guess at a circuit, the tab nearest to the devices is common to both, and each of the other two tabs goes to one device. For example, back on the main controller, the common tab goes to GND; the LED tab goes to a current-limiting resistor, and that goes to Vcc; and the photodiode tab goes to a pull-up resistor and a comparator. Or something like that.

Without tests, there is no way to know if the LED is on continuously, pulsed only when a cycle starts, or whatever. The cameras in phones and tablets can see and display the IR light from most tv remotes, and probably can show you if the LED is on. My guess is that it is pulsed to increase the systems immunity to ambient light giving a false reading.

ak

 

[HitMan]

Awesome thank you here is a picture of the symbol not sure you can make it out

 

[Harald Kapp]

The top symbol is a transistor, indicating the receiver side of the pair.
The bottom symbol is a diode, indicating the transmitter side of the pair.

What makes you think this component is defect? That would be rare as these components are rather sturdy.
Sensors of this type are fairly common, see e.g. here.

 

[HitMan]

You’re absolutely amazing that’s exactly the one……not sure it will fix but for 5$ it’s worth a try….I will give you a update once completed…Thank you be in touch in a few days