BEAM robot IC swap - Page 1
Forum section: electronics / beginners

author: Lucky-Luka
author_rank: Unknown
timestamp: June 05, 2022, 02:07:23 pm
content: Hi allI was looking at this kind of photopopperhttp://solarbotics.net/library/circuits/se_t1_1381.htmlIs there a newer alternative to this kind of IC (MN1381-x)?Thanks

author: rstofer
author_rank: Super Contributor
timestamp: June 05, 2022, 03:27:42 pm
content: 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/1465093It is a voltage supervisor device, just a simple 3 terminal component.

author: ledtester
author_rank: Super Contributor
timestamp: June 05, 2022, 03:30:47 pm
content: 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=pricingIf 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".

author: Lucky-Luka
author_rank: Unknown
timestamp: June 05, 2022, 03:48:45 pm
content: It looks like MCP101-315HI/TO IC will do the trick.Thanks

author: Lucky-Luka
author_rank: Unknown
timestamp: June 16, 2022, 08:29:02 am
content: Quote from: ledtester on June 05, 2022, 03:30:47 pmI 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...

author: ledtester
author_rank: Super Contributor
timestamp: June 16, 2022, 10:55:01 am
content: 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.htmlIt 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.

author: Lucky-Luka
author_rank: Unknown
timestamp: June 16, 2022, 11:03:43 am
content: is it clear from the datasheet the behaviour that I mentioned above?

author: ledtester
author_rank: Super Contributor
timestamp: June 16, 2022, 02:43:25 pm
content: 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.

author: Lucky-Luka
author_rank: Unknown
timestamp: June 16, 2022, 06:11:49 pm
content: Is the position of the motor correct?