BEAM robot IC swap

[Lucky-Luka]

Hi all
I was looking at this kind of photopopper
http://solarbotics.net/library/circuits/se_t1_1381.html
Is there a newer alternative to this kind of IC (MN1381-x)?
Thanks

[rstofer]

I'm not going to run through the datasheets but there is a similar IC at Digikey:

https://www.digikey.com/en/products/detail/panasonic-electronic-components/MN13812SGU/1465093

It is a voltage supervisor device, just a simple 3 terminal component.

[ledtester]

Mouser still carries TO-92 package voltage supervisors. Try this link:

https://www.mouser.com/c/semiconductors/power-management-ics/supervisory-circuits/?q=pmic&mounting%20style=Through%20Hole&output%20type=Active%20High%2C%20Push-Pull&package%20%2F%20case=TO-92~~TO-92-3&rp=semiconductors%2Fpower-management-ics%2Fsupervisory-circuits%7C~Package%20%2F%20Case&sort=pricing

If it doesn't work for you, go to:

https://www.mouser.com/c/semiconductors/power-management-ics/supervisory-circuits/

and select "Through-Hole", "TO-92" package, "Active High, Push-Pull".

[Lucky-Luka]

It looks like MCP101-315HI/TO IC will do the trick.
Thanks

[Lucky-Luka]

and select "Through-Hole", "TO-92" package, "Active High, Push-Pull".

I think I have to buy the active low version of this kind of IC: I have bought active high MCP101 and it acts in the opposite way that I wanted since the output is equal to the input until it reaches the threshold and then it goes to zero...

[ledtester]

It seems what you bought should work in an "upside down" version of the BEAM circuit which exchange NPN and PNP transistors. Although this is kinda an off-the-cuff remark and I haven't tried drawing it out.

The original BEAM circuit:



Update: The two transistors in the original BEAM circuit form a discrete thyristor. Once the 1381's output goes high for even a little bit the PNP keeps base current flowing into the NPN even if the 1381's output goes low. This continues until the cap is depleted.

Here's a page on the two-transistor analogy for a thyristor:

https://www.electronics-tutorials.ws/power/thyristor.html

It shows the thyristor being triggered at the base of the NPN. But you can also trigger it by bringing the base of the PNP low. In this case you'd move the motor to the low side of the circuit.

[Lucky-Luka]

is it clear from the datasheet the behaviour that I mentioned above?

[ledtester]

Here's the "upside down" version of the Beam circuit:



When the output of the voltage detector goes LOW it will open the PNP transistor setting everything into motion.

[Lucky-Luka]

Is the position of the motor correct?