# Hall Effects Switches

#### SmokedCircuit64

May 12, 2011
13
So... Here goes my first stab at things..

I need a triggering/switch type device for a project.. The first thing that came to my mind was a Hall Effect switch because I have moving parts and they can’t touch but need to interact. I will be using a 12 VDC supply to trigger an electromagnet. I don’t want constant current supplied; rather I need a timed pulse of current to activate, then turn off until it is needed again.

My thought path.. 12 VDC in, current remains at the ready till switch allows current to flow and activate electromagnet then turns off current. Kinda like a regular light switch!
My issue is that I have NO IDEA what type of hall effect switch I need to look for.. I have seen switches that can take 4 to 24 VDC of input, but the output always seems to be way less than what I need or doesn’t equal the input.

Thanks for the assistance.
Kevin

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
In general the hall effect switch would control a device like a MOSFET which would switch a larger current.

#### SmokedCircuit64

May 12, 2011
13
In general the hall effect switch would control a device like a MOSFET which would switch a larger current.

What would a circuit look like that has the MOSFET and hall effects working together? Is there a name for that type of switching circuit?

#### poor mystic

Apr 8, 2011
1,074
Hi SmokedCircuit
How fast will the switching need to happen, and at what frequency, please?

Ohh, your new post just came in so I'll edit:
You question: "What would a circuit look like that has the MOSFET and hall effects working together?"

Generally speaking, the current from the Hall Effect device is made to control a transistor or similar current-amplifying device. Sometimes, that general statement is wrong, it is the voltage which does the controlling. Too confusing.

Please pick a Hall-effect device for your example, and I for one will try and design and post a circuit for it. Do please remember to say how often the device will get triggered (how fast does your shaft or whatever rotate).

See ya then
:-D

(PS I've smoked a few circuits myself but perhaps I'd prefer to smoke fish)

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#### SmokedCircuit64

May 12, 2011
13
Poor Mystic,
I am a total new-bee with this stuff.. Mechanical stuff I can make dance, but anything electronics wise I just make smoke.. Hence the user name.. LOL

I'll explain my ideas.. So i have a flywheel roughly 6" dia.. I thought I would just drill and insert a small magnet into the flywheel at a position just after TDC to trip the hall effect switch which would then fire the coil.. "steve" said I need a MOSFET to do the switching and the hall effect to trigger the MOSFET.

So you asking me the speed I need this to happen is something I really don't understand.. If I had to take a stab at it, I would guess a few mili-seconds.

Will any hall effect work? and where can I find then to pick you one out..

Sorry if this isn't as simple as it should be.. But I really thank you for your assistance..

Kevin

#### poor mystic

Apr 8, 2011
1,074
So, SmokedCircuit! :-D
sounds like you're building an electronic ignition. As far as I know it is very easy to design an electronic ignition system that is unreliable and a plain hassle.
Have you considered using the electronic ignition sets already on the market?

#### SmokedCircuit64

May 12, 2011
13
Here is the info on it:
SENSITIVE HALL-EFFECT SWITCHES FOR HIGH-TEMPERATURE OPERATION A 3144 E 44
A3144E
this item will not be supplied shipping tracking number if you want tracking number please pay extra 1.5 us dollar!

please send us an email to confirm for needing tracking number as soon as you order it . and please set confirmed

address in paypal other wise we will not send out before we get confirmed address

These Hall-effect switches are monolithic integrated circuits with
tighter magnetic specifications, designed to operate continuously over
extended temperatures to +150°C, and are more stable with both
temperature and supply voltage changes. The unipolar switching
characteristic makes these devices ideal for use with a simple bar or rod
magnet. The four basic devices (3141, 3142, 3143, and 3144) are
identical except for magnetic switch points.
Each device includes a voltage regulator for operation with supply
voltages of 4.5 to 24 volts, reverse battery protection diode, quadratic
Hall-voltage generator, temperature compensation circuitry, smallsignal
amplifier, Schmitt trigger, and an open-collector output to sink
up to 25 mA. With suitable output pull up, they can be used with
bipolar or CMOS logic circuits. The A3141– and A3142– are improved
replacements for the UGN/UGS3140–; the A3144– is the
improved replacement for the UGN/UGS3120–.
The first character of the part number suffix determines the device
operating temperature range. Suffix ‘E–’ is for the automotive and
industrial temperature range of -40°C to +85°C. Suffix ‘L–’ is for the
automotive and military temperature range of -40°C to +150°C. Three
package styles provide a magnetically optimized package for most
applications. Suffix ‘–LT’ is a miniature SOT89/TO-243AA transistor
package for surface-mount applications; suffix ‘–U’ is a three-lead
plastic mini-SIP, while suffix ‘–UA’ is a three-lead ultra-mini-SIP.

FEATURES and BENEFITS
Superior Temp. Stability for Automotive or Industrial Applications
4.5 V to 24 V Operation … Needs Only An Unregulated Supply
Open-Collector 25 mA Output … Compatible with Digital Logic
Reverse Battery Protection
Activate with Small, Commercially Available Permanent Magnets
Solid-State Reliability
Small Size
Resistant to Physical Stress

ABSOLUTE MAXIMUM RATINGS
at TA = +25°C
Supply Voltage, VCC ............................ 28 V
Reverse Battery Voltage, VRCC ........... -35 V
Magnetic Flux Density, B .......... Unlimited
Output OFF Voltage, VOUT .................. 28 V
Reverse Output Voltage, VOUT ........... -0.5 V
Continuous Output Current, IOUT ...... 25 mA
Operating Temperature Range, TA
Suffix ‘E–’ .................. -40°C to +85°C
Suffix ‘L–’ ................ -40°C to +150°C
Storage Temperature Range,
TS .............................. -65°C to +170°C

ELECTRICAL CHARACTERISTICS at VCC = 8 V over operating temperature range.
Limits
Characteristic; Symbol ;Test Conditions ;Min. Typ. Max. Units
Supply Voltage ;VCC; Operating; 4.5 -- 24 V
Output Saturation Voltage ;VOUT(SAT); IOUT = 20 mA, B > BOP ;-- 175 400 mV
Output Leakage Current ;IOFF; VOUT = 24 V, B < BRP; --<1.0 10 UA
Supply Current ;ICC; B < BRP (Output OF—F);- 4.4 9.0 mA
Output Rise Time ;tr; RL = 820 Ω, CL = 20 pF ;— 0.04 2.0 Us
Output Fall Time ;tf; RL = 820 Ω, CL = 20 pF ;— 0.18 2.0 Us

MAGNETIC CHARACTERISTICS in gauss over operating supply voltage range.
Characteristic Min. Typ. Max.
BOP at TA = 25°C Min.70 Typ.-- Max.350
over operating temp. range Min.35 Typ.-- Max.450

BRP at TA = 25°C 50 — 330
over operating temp. range 25 — 430

Bhys at TA = 25°C 20 55 —
over operating temp. range 20 55 —

I have no idea what any of that means!

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#### SmokedCircuit64

May 12, 2011
13
So, SmokedCircuit! :-D
sounds like you're building an electronic ignition. As far as I know it is very easy to design an electronic ignition system that is unreliable and a plain hassle.
Have you considered using the electronic ignition sets already on the market?

es your correct.. Thanks.. I'll do a search

#### poor mystic

Apr 8, 2011
1,074
wow
ok so don't examine me too closely either... "quadratic Hall-voltage generator" tells me I have reading to do.
But I see nothing here to be skeptical about. Looks a lot easier than homemade that's for sure.
Is this equipment very expensive?

#### SmokedCircuit64

May 12, 2011
13
You told me to go find one and let you know, so I went to eBay (as usual when I'm looking for something) I need.
http://cgi.ebay.com/10-HALL-EFFECT-...&otn=3&po=LVI&ps=63&clkid=9111164710449887466

it is like $10 for 10 of them.. So I take it I found something good? Oh Yeah I found a a site where a guy sells a kit for$22 - \$26 depending on the bells and whistles you want..
http://www.jerry-howell.com/IgnitionModules.html
I just need to ask him if he can rework it for 12 volts..

Apr 8, 2011
1,074

#### SmokedCircuit64

May 12, 2011
13
Which do you think would be the best way to go?
Using the hall effect switches I posted the info for or to go with the circuit kit Jerry Howell has?

#### poor mystic

Apr 8, 2011
1,074
well I got a 404 when I followed the first link so Jerry wins by default I guess

#### SmokedCircuit64

May 12, 2011
13
So the ebay link didn't work? I was trying to save you the time in searching for it by using the link..
If you just got to ebay abd put the item number in the search box you should be able to get there..

Item number: 140509114859

Hope that works for you!

#### poor mystic

Apr 8, 2011
1,074
Hi SC
OK, those look like good detectors... you want a timed pulse?
You need to know how to build a single-pulse generator, also called a monostable vibrator.
You need to trigger the monostable with the Hall-Effect device, and the monostable o/p controls a power transistor.

There are 3 stages to the circuit I imagine you want
1) Hall-Effect device
2) monostable
3) power output

How will you design your monostable?

PS But I think you're better off with Jerry

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#### SmokedCircuit64

May 12, 2011
13
I think your right.. I'll go with the JEH Circuit Kit. At this point in my learning curve, I need to study how it functions before I can attempt some other sort of design. The kit will have all the parts needed so I will always have a reference once i'm ready to interduce mods to it.

Thanks for the help..

now if I could get some concrete info and or feed back on building an elecrtomagnet based off my idea I would be off to a running start.

Thanks again
SC

#### SmokedCircuit64

May 12, 2011
13
Here I am full of questions again.. LOL
I was just thinking..

So the JEH Circuit kit is for a 6 volt system.. What would have to be done to it for it to be used with 12 volts?

#### poor mystic

Apr 8, 2011
1,074
Ask the guys at JEH, whose opinion comes with a guarantee!

#### SmokedCircuit64

May 12, 2011
13
Well.... They haven't returned my email yet! I may be back at square one again. So, planning on not ever hearing back from JEH.
I have a few questions..
1) What MOSFET type would I need?
2) What Hall Effects Switch type do I need?
3) What other items are required to build the circuit?

The circuit needs to run on 12 volts. The circuit seems simple enough to lay out. I could probably just burn it up once if I'm lucky.. LOL

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