Voltage Surge Suppression from Hall Effect Sensor Transient Response
Voltage Surge Suppression from Hall Effect Sensor Transient Response
(OP)
Hello all,
I am working with a "Hamlin 55100" Hall effect sensor (actually two of them with overlapping output signals 5V->~0V->5V), whenever I trigger the two hall sensors with a magnet I get a really ugly pulse (as seen in photo). At the end of the pulse there is a transient response that shoots the voltage up to 8V then resonates for a bit at 6V. I'm trying to remove this voltage surge and the resonating effect that happens afterwards. I looked into using a MOV, but as far as I can tell the MOV would not survive the amount of cycles it will experience (I'm planning on exposing it to over 250,000pulses).
The Hamlin 55100 spec sheet says to use a capacitor between the positive and negative wires of the sensor (but they don't specify a size), I've already blown up one capacitor (470uF) in my face trying this but with little to no success. ---I'd prefer not to experience the exploding capacitor again ---
please help if you can.
Thanks.
I am working with a "Hamlin 55100" Hall effect sensor (actually two of them with overlapping output signals 5V->~0V->5V), whenever I trigger the two hall sensors with a magnet I get a really ugly pulse (as seen in photo). At the end of the pulse there is a transient response that shoots the voltage up to 8V then resonates for a bit at 6V. I'm trying to remove this voltage surge and the resonating effect that happens afterwards. I looked into using a MOV, but as far as I can tell the MOV would not survive the amount of cycles it will experience (I'm planning on exposing it to over 250,000pulses).
The Hamlin 55100 spec sheet says to use a capacitor between the positive and negative wires of the sensor (but they don't specify a size), I've already blown up one capacitor (470uF) in my face trying this but with little to no success. ---I'd prefer not to experience the exploding capacitor again ---
please help if you can.
Thanks.





RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
You cannot possibly blow up a capacitor with that voltage - unless you had the wrong polarity.
A MOV is a bad choice here. For many reasons.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
The hall sensor is attached to an electronic ignition system(EIS) that takes ~10mA (open collector input pretty sure) and a National Instruments DAQ system that requires minimal amperage if any.
It's interesting you say an inductive kick-back, the ignition system is controlled by a microprocessor, is it possible that there's too much current going to the ignition system currently? I did add three 1K resistors in parallel (to make a 333ohm resistor since I had none), to limit the current going to the ignition system. At 12V and 333ohms, the current should be 0.036A going to the EIS. If the EIS needs more current could it induce a "kick-back"?
RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
> EMI noise feeding into your scope
> ground bounce from the firing the spark plug
See: http://mgaguru.com/mgtech/ignition/ig108.htm for similar voltage waveform.
TTFN
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RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
The Hall effect sensor itself is probably very small (physical size) and would thereby be relatively insensitive to EMI itself. But the wiring running from the sensor to the input of the processor needs to be protected using basic E3 design techniques (twisted pair, shields, isolated signal return path).
RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
Hi IRstuff, Thanks for the link to the file its interesting because the ignition system sparks right at the rising edge of the hall sensor pulse (therefore probably the reason for the effects seen). When you mention ground bounce... is there a way to prevent this? I'll increase the diameter of wire going to ground, maybe it will help.
I should also let people know that I am seeing low voltage spikes in other measurements (pressure transducer and optical encoder).
RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
The test would be when you disconnect the ignition coil, you get a clean signal. How far from the ignition coil are the Hall sensors?
TTFN
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RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
Unfortunately I'm off-site today, but tomorrow I will try it all out and let you know what ends up happening. Any last suggestions for stuff to try before tomorrow? I have already removed the following wiring issues: removed extra current loops, wire loops, wire separation minimum of 1ft between switching and analog signal wires. And I've added the following to the circuit: twisted pairs, shields, ground isolation. One item I haven't added (for reasons seen in my initial post) is the capacitor between the circuits and the ground, or between the positive/negative terminals of the loads. I have heard a few times that it helps in relieving transient responses, although my knowledge in sizing these is minimal.
I guess for some reason I was convinced earlier it had to do with the hall sensor but I'm starting to believe that it could be due to the ignition system.
RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
The 10nF capacitor should be placed between the signal and ground or the power and ground? The spec sheet recommends one between the Power and Ground wires (specsheet attached), but they do not give a size.
RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
TTFN
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RE: Voltage Surge Suppression from Hall Effect Sensor Transient Response
(actually two of them with overlapping output signals 5V->~0V->5V)
And your waveforms troubling. I suspect you are doing something with these sensors that we can't even imagine. Could you show how these sensors are hooked up?