Hall Effect Switch Design - Page 1
Forum section: electronics / beginners

author: Falcon69
author_rank: Super Contributor
timestamp: March 05, 2014, 06:37:22 am
content: Hello,I think I have finished my design, and it seems to work fine on the prototype breadboard. I used the actual components. I bought some adapter boards for the SMD components and used those.The RED box is my existing switches that I have made up already. The circuit in the green box would be an add-on circuit board to select normally closed and normally open option, as well as making it so there is a two wire configuration going to the breakout board, as if a mechanical switch was wired to the breakout board. The normally closed option makes it so if the limit switch was cut or disconnected, it would become a safety factor and break the connection in the breakout board, which in turn would send a signal to the software to shut the machine down. The normally closed option allows the switches to be wired in series. The normally open option doesn't give that safety factor, but would allow other switches to be wired in parallel.The area in grey would be the length of the wire, up to 30 feet and on very rare instances, 50 feet.Now, on the breadboard, it works as intended, but, before I have the circuit boards fabricated, anyone have any suggestions? Both to the area in the red box, and more importantly, the area in the green box?Thanks in advance for any help.Jason

author: Falcon69
author_rank: Super Contributor
timestamp: March 05, 2014, 08:08:15 am
content: I also wanted to ask,I will be using braided shielded wiring with this switch. Do I need to connect the braided part to ground, or just leave it unconnected? It would be easier unconnected, as that is one less hole to make space for, but if it needs to be connected, then it will be.

author: fcb
author_rank: Super Contributor
timestamp: March 05, 2014, 09:23:04 am
content: 1. The SS441A is capable of sinking 20mA continuosly (datasheet) - my estimate is your pulling 30mA through the part with your 100ohm dropper resistor. Use a more efficient LED - back the current down.2. You short out the other LED with the transistor - whilst it will work, it isn't common practice as it's wasteful of power. Switch the LED with the transistor, use a PNP to get your logic right.3. The XOR/switch is a neat way to do things, but I wouldn't bother unless you want to grandstand. I'd just invert the signal with transistors and give a 2nd output.4. You can reverse the input logic in Mach3, why bother doing it on the board.5. Put the 2nd output on the sensor board? Reduce down to one LED.All in, I think you have a complicated solution to a simple product - however these extra 'features' might be what you need to sell this - what do I know..

author: Falcon69
author_rank: Super Contributor
timestamp: March 05, 2014, 05:35:26 pm
content: Quote from: fcb on March 05, 2014, 09:23:04 amhmm, simulation shows 19.89mA through it.QuoteA PNP transistor doesn't seem to work in simulation, a NPN does to switch on the green LED. What do you mean by get your logic right?QuoteWhat do you mean by grandstand? If I do a second output, that means another 2 wires. that would mean I'd need a 6 core wire coming out of the second circuit board. I want two circuit boards, because for 1: There's only a 3 core wire going to the machine for that long distance, 3-core is cheaper, and 2: there is a capacitor on the second board that will be on the other end of that long wire which would help with noise issues and possible false triggers do to the noise.QuoteI need to do it on the board, because the Gecko G540 works off an optocoupler. In order to have the safety factor if the wire is cut or disconnected, it would cut that Optocoupler LED off, thus sending a signal to Mach3. If I make the whole switch normally open, it will not do that. The optocoupler would be off in normal operation mode and on when tripped. If a switch is cut or unplugged, that optocoupler would remain in the off state. no signal would be sent to Mach3 for it to reverse the logic input. Or maybe I don't understand what you are suggesting?QuoteI want two LED's. Green for on status, Red for tripped. If I put the output on the sensor board, again, that 4-core wire going to the machine from the control box. that's more expensive wiring, and, i will not have a capacitor on the other end to help with noise.The other problem I have is that I already have nearly 100 of these switches made. I am trying to fix what I already have made. The data sheet for the ss441a also says it can sink up to 50mA momentarily. Seeing how the RED LED is not continuously on and only goes on for a brief second when the limit is tripped and the machine backs off, it should be okay, right?

author: fcb
author_rank: Super Contributor
timestamp: March 05, 2014, 05:47:41 pm
content: Quote from: Falcon69 on March 05, 2014, 06:37:22 amQuote from: Falcon69 on March 05, 2014, 05:35:26 pm?

author: London Lad
author_rank: Regular Contributor
timestamp: March 05, 2014, 05:58:41 pm
content: Quote from: fcb on March 05, 2014, 09:23:04 am^^^

author: Falcon69
author_rank: Super Contributor
timestamp: March 05, 2014, 06:36:29 pm
content: fcb, I already have the switches made (the circuit board in the Red Box). I need to have the circuit board in the Green box made. I will later, make it all on one board, but for now, I'm trying to save what I have.

author: fcb
author_rank: Super Contributor
timestamp: March 05, 2014, 06:48:28 pm
content: The 1M to gnd on the XOR. I would replace that with a pull-up resistor (4K7 to your +5V), you'll get a much cleaning switching action.Make sure you power your XOR also - couldn't see the Vcc/Vss connections.Also, just use a regular XOR (74HC86), you can use the other 3 elements for the other channels.

author: Falcon69
author_rank: Super Contributor
timestamp: March 05, 2014, 09:24:15 pm
content: Thanks fcb, I'll play around with it on the simulation and see what I come up with.

author: Ivanko1
author_rank: Contributor
timestamp: July 28, 2014, 10:53:17 pm
content: Hi! I need simple scheme for switch off the MOSFET on hall effect. Only hall switch, transistors, resistors and capacitor maybe.)Rule is simple: when there is no magnetic field (MF) - MOSFET must be on, then MF is present - MOSFET must be OFF as quickly as possible, and than MF dissapear - MOSFET must be on again.I want create something like Ruhmkorff Coil, but wihout moving parts.https://www.youtube.com/results?search_query=Ruhmkorff+coilI have hall sensor 3144 oh 09http://www.princeton.edu/~mae412/TEXT/NTRAK2002/161-168.pdfand IRF840http://www.st.com/web/en/resource/technical/document/datasheet/CD00000705.pdfmy primary coil about 60 Ohms, 12 VoltsSimple 3144 work: then no MF - on pin out is 6 volts (1/2 VCC), then MF present - its 0 (low).I connect pin out to gate directly - they work, but both begining to start hot (keep my finger) about 1 minute, oscillate not permanent - getting low and stop.I think - there must be at least a couple of resistors?Can you help me please?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 29, 2014, 02:08:02 am
content: EMC: I'd like to see a series R on that logic input (from the cable, going into the XOR), and a cap to GND, to filter possible RF. This explicitly slows logic transitions (you don't need the equivalent bitrate / response time, so that's okay, operationally speaking), so you should have a Schmitt trigger as well (e.g. 74HC1G14, or the TinyLogic(r) equivalent if you prefer).It should also have a TVS diode or something like that, which isn't necessarily a hard requirement if you've got a resistor in there. But the most critical condition will be, suppose someone's randomly plugging these circuits together, it's a cold dry winter day, lots of static electricity around... a cable being pulled through a conduit picks up a good 20kV, wire touches circuit...POW, bye bye logic gate. Easy enough to avoid these kinds of situations. Don't forget that it can happen on either end, too; whether you want a TVS on the Hall effect sensor board kind of doesn't really matter, say if it's more disposable than the rest, but maybe you'll want it for good practice anyway (one across the +5V supply to GND would be prudent as well).Tim