Truncation: IC recommendations for driving many electromagnets + shift registers - Page 1
Forum section: electronics / beginners

author: Cranberry
author_rank: Contributor
timestamp: February 24, 2016, 11:40:55 pm
content: Hi Everyone,As a recap, I've been essentially working on a project similar to this:http://www.instructables.com/id/How-to-Control-an-Electromagnet-with-an-Arduino/. Ended up taking another member's advice to do a bunch of shift registers and MOSFETs to control 18 electromagnets with an LM350 voltage regulator.The circuit draws a considerable load at 5V regulation with each electromagnet being about 6 ohms each (maxes out around 3A for 18 when doing pulses). The electromagnets go in one direction only instead of two, each electromagnet operates in parallel has its own MOSFET.The circuit has 18 MOSFETs, 1 voltage regulator, 3 shift registers.If I wanted to try my hand at making a PCB, what are my options in terms of ICs that could shrink the board down in size?Are there ICs I could buy that combines 4 separate MOSFETs onto a single chip that can support a total current load of say 700~1A (so approx 0.18~0.25 A per load * 4)? Or something that combines shift registers + MOSFETs that can support that kind of load?

author: HwAoRrDk
author_rank: Super Contributor
timestamp: February 24, 2016, 11:53:24 pm
content: Many motor driver ICs are suitable for driving solenoids. Something like the L298 has plenty of current capability and can drive 4 solenoids.

author: michaeliv
author_rank: Frequent Contributor
timestamp: February 25, 2016, 12:07:47 am
content: What is your current design ? Get it smaller than what ?I imagine it would be very difficult, impractical and not cost effective to get it smaller than 1x20-32 bit shift register +18 individual SOT-23 AO3401. Especially since you can easily place the MOSFETs as individual components. But even then most of the board size would probably go to making the connections to the solenoids.

author: Cranberry
author_rank: Contributor
timestamp: February 25, 2016, 06:32:13 am
content: Quote from: michaeliv on February 25, 2016, 12:07:47 amThat's a great idea. What about:http://media.digikey.com/pdf/Data%20Sheets/Microchip%20PDFs/HV9308,9408.pdffor a shift register andhttp://www.nxp.com/documents/data_sheet/BUK78150-55A.pdfN-ch MOSFETs?Current design is breadboarded with 18 IRLB8721PbF MOSFETs, LM350+heatsink, 3 74hc595 shift registers and a bunch of diodes in parallel with some solenoids. I hope that helps.

author: michaeliv
author_rank: Frequent Contributor
timestamp: February 25, 2016, 08:15:43 am
content: The driver seems good, but comes in PLCC form, which is not at all good if you're trying to save board space. The MOSFETs have RDS(ON) of 150mOhm. I would recommend trying to find one with lower on impedance. The reason I suggested the AO3401 is because they have RDS(ON) of 45mOhm and are very cheap when ordered from China (3c in 100 qty).If this is a one-off build you probably don't care about cost, so you might as well go with what is available, but try to keep the On resistance small to not unnecessarily overheat the MOSFETs.

author: Cranberry
author_rank: Contributor
timestamp: February 25, 2016, 02:59:51 pm
content: @PLCC form: which ones may be better in terms of packaging?Also:http://aosmd.com/res/data_sheets/AO3400A.pdfdoesn't seem so bad.

author: michaeliv
author_rank: Frequent Contributor
timestamp: February 25, 2016, 03:20:34 pm
content: QFP / QFN would be the small er choices.Yes, I actually meant the AO3400 before, not the AO3401, I confused the P-Version with the N-Version, You need the AO3400, N-channel ONE.

author: Cranberry
author_rank: Contributor
timestamp: February 26, 2016, 02:38:24 am
content: Good to find the right mosfet. Totally by chance.http://ww1.microchip.com/downloads/en/DeviceDoc/hv5523.pdf?

author: michaeliv
author_rank: Frequent Contributor
timestamp: February 26, 2016, 03:41:31 am
content: That shift register seems good, yes.

author: Cranberry
author_rank: Contributor
timestamp: March 08, 2016, 10:18:58 pm
content: A little late, but thank you to everyone who replied.