1st homemade light from scratch- sst90 aspheric H2O proof - 10 AMPS build log

[wquiles]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

Ahh. Now with the diagram things make sense to me

According to the data sheet of the Hall switch (page 4 of 12, lower right picture for the UA package), its output pin goes LOW (to GND) when it feels the South pole within the active range, so if your MOSFET was an N-channel, which was waiting for a HIGH (Battrery +) at the GATE to turn ON, it would never turn ON. If you can let me know the exact part number of the MOSFET(s) you were trying it would be very helpful to verify this.

From your diagram it looks like you have a PNP Darlington, which makes sense it works, since it needs a LOW signal to turn ON. This Wiki page has a good explanation and pictures of the various types of bipolar and FET transistors:
http://en.wikipedia.org/wiki/Transistor

Note that although you have this setup working and it is not getting warm, the right MOSFET will have an even lower ON resistance, therefore working even better as a true switch than the Darlington (or any other bipolar) ever could.

Then again it is hard to argue with a working solution. If you test it with the highest possible current you will ever see, for extended periods of time, and it does not get too warm/hot, then consider it a good circuit and move on with the rest of the project

 

[gt40]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

What is your supply voltage?
Which hall effect sensor are you using?
Which MOSFET are you using?

Im studying electrical engineering, so i might be able to locate your problem.

For this light, (1) 26650 3.7v battery space

Hall effect sensor: http://www.simplemotor.com/hallswitch.htm

I have a bunch also from digikey with different specs.

Mosfet: IRLZ34

I would really appreciate any help you can offer. I am pretty frustrated after having the darlington, simple motor hall sensor combo work and then killing 2 sets putting it in the light with my newbie soldering... (different issue) Basically, the darlington combo started turning on the led barely visable even when the magnet wasnt there. Prefer n based mosfet that will turn on with a hall effect sensor and handle 10 + amps and work every time.

 

[wquiles]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

Prefer n based mosfet that will turn on with a hall effect sensor and handle 10 + amps and work every time.

If I am reading the data sheet of the Hal sensor correctly, the output goes LOW when the magnet is in range. Can you please verify this behavior?

If that is the case, that the Hall sensor outputs a low (close to GND or Bat "-"), then you can't use an N-channel MOSFET since the N channel needs a high voltage from Gate to Source to turn ON, and since the Hal sensor you are using gives you the opposite. This is why the PNP Darlington works, since it needs the low voltage to turn ON.

 

[gt40]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

If I am reading the data sheet of the Hal sensor correctly, the output goes LOW when the magnet is in range. Can you please verify this behavior?

If that is the case, that the Hall sensor outputs a low (close to GND or Bat "-"), then you can't use an N-channel MOSFET since the N channel needs a high voltage from Gate to Source to turn ON, and since the Hal sensor you are using gives you the opposite. This is why the PNP Darlington works, since it needs the low voltage to turn ON.

I haven't been able to verify it because I killed the simple motors hall effect sensor re soldering it. I also wasn't able to find any data sheet there, only the description link which I already posted.

I did however try the infineon unipolar TLE4905L with the IRLZ34
and it didn' turn it on. Here is the link to the data sheet for that one:

http://media.digikey.com/pdf/Data Sheets/Infineon PDFs/TLE4905L, 06L, 45L, 45-2L.pdf

Any suggestions would be appreciated.

 

[b-bassett]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

hi all
this may be completely wrong but i think i read somewhere that some hall effect sensors will output low when a south pole is used will output high when a north pole is used.

might be worth a shot?

 

[gt40]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

hi all
this may be completely wrong but i think i read somewhere that some hall effect sensors will output low when a south pole is used will output high when a north pole is used.

might be worth a shot?

I tried both poles

I guess I need a hall sensor that outputs positive voltage when it gets close to the magnet and sufficient to turn on the gate. I am reading greek though looking at all these data sheets...

 

[wquiles]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

I have not done an exhaustive search, but for the little I have found searching on Digikey, it seems that most Hall sensors are designed to output LOW/GND when the magnet is in the active area.

 

[gt40]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

Here are some diagrams for the 3 version of circuits I am trying to make work:

Reed switch version:

Finally, the darlington pnp version would look just like the chart above except for the following:

substitute irz34 mosfet for darlington pnp-

Gate= base
collector= source
emitter= drain

I would like to find a hall sensor that outputs "high" and will work with the mosfet. Not sure what to do at this point..

On another note, I also found this circuit in instructables but still trying to understand the other components. It seems to use a "latching" sensor: http://www.instructables.com/id/Door-Activated-LED-Lighting-using-Hall-Effect-Sens/

Final question: I have found a number of hall effect sensor circuits referencing "pull up" resisters in the circuit. could this be the missing piece?

In any case I am having a bunch of darlington transisters and hall effect switchs I got to work in the original working circuit overnighted and will do some real testing of them after more carefully soldering a new circuit. I found it is easy to burn them if you keep the soldering tip on for too long.

 

[MikeAusC]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

I would like to find a hall sensor that outputs "high" and will work with the mosfet. Not sure what to do at this point..


Final question: I have found a number of hall effect sensor circuits referencing "pull up" resisters in the circuit. could this be the missing piece?

.

All the Hall Effect switches I've seen are NPN Open-Collector output - when activated by a magnet the Output gets pulled to ground.

If you're driving a FET from an NPN Open Collector output, you must have a pullup resistor (Output to +) because there's nothing to pull the output above ground when not switched on.

You must never have the Gate of a FET open-circuit - the voltage could drift anywhere.

You can only connect a P-channel FET directly to an NPN Open-Collector output. The FET Drain connects to Batt +.

To use an N-channel FET (most are N channel) you need to use a PNP transistor as an Inverter - Emitter to Batt+, Collector to a 10k Resistor to ground and the FET Gate.

 

[IMSabbel]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

I do not want to be annoying, but:

Do you plan on adding a plane window in front of the aspheric? Because you realize that if not, it will not work l underwater because of the index of refraction mismatch between the curved side of the aspheric and the water?

 

[SirJMD]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

For this light, (1) 26650 3.7v battery space

Hall effect sensor: http://www.simplemotor.com/hallswitch.htm

I have a bunch also from digikey with different specs.

Mosfet: IRLZ34

I would really appreciate any help you can offer. I am pretty frustrated after having the darlington, simple motor hall sensor combo work and then killing 2 sets putting it in the light with my newbie soldering... (different issue) Basically, the darlington combo started turning on the led barely visable even when the magnet wasnt there. Prefer n based mosfet that will turn on with a hall effect sensor and handle 10 + amps and work every time.

Kinda need a model name on the HE sensor - the link just explains how the HE sensor works. But if it is like some says, you probably have to use a P-channel MOSFET instead (tho i dont like those - their RON is often much worse than N-channel).

Regarding the MOSFET - you might want to find one with a lower RON, else youre gonna loose quite some power there. Since you dont need to swich more than around 4V, a 60V MOSFET is overkill - the lower the voltage rating, the lower the RON is (in general).

 

[gt40]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

MikeAusC wrote:

All the Hall Effect switches I've seen are NPN Open-Collector output - when activated by a magnet the Output gets pulled to ground.

If you're driving a FET from an NPN Open Collector output, you must have a pullup resistor (Output to +) because there's nothing to pull the output above ground when not switched on.

You must never have the Gate of a FET open-circuit - the voltage could drift anywhere.

You can only connect a P-channel FET directly to an NPN Open-Collector output. The FET Drain connects to Batt +.

To use an N-channel FET (most are N channel) you need to use a PNP transistor as an Inverter - Emitter to Batt+, Collector to a 10k Resistor to ground and the FET Gate.

Kinda need a model name on the HE sensor - the link just explains how the HE sensor works. But if it is like some says, you probably have to use a P-channel MOSFET instead (tho i dont like those - their RON is often much worse than N-channel).

Regarding the MOSFET - you might want to find one with a lower RON, else youre gonna loose quite some power there. Since you dont need to swich more than around 4V, a 60V MOSFET is overkill - the lower the voltage rating, the lower the RON is (in general).

Thanks for the input. I am kinda over my head here and would really appreciate any guidance anyone can offer. I just want to make a switch design for multiple lights that will work on sst90 level power and turn on with an hall effect sensor.

Would something like this work:

http://www.onsemi.com/pub_link/Collateral/MTP50P03HDL-D.PDF

Or this: http://www.toshiba.com/taec/components2/Datasheet_Sync//78/2948.pdf

Or finally this one: http://www.vishay.com/docs/70766/70766.pdf

Also, I am still trying to get my head around what the circuit would look like.

As far as hall effect sensors, I have some of these: http://media.digikey.com/pdf/Data%20Sheets/Infineon%20PDFs/TLE4905L,%2006L,%2045L,%2045-2L.pdf

The 4905L's. Would this work?

Thanks again for the info in advance...

 

[SirJMD]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

As far as the HE sensor goes, its active low. This means that the output is inverted of what you would normally experience (normally its: on = high. But not here).

Solution is either a P-channel MOSFET, or a N-channel and an inverting gate driver - such as the TC4426.

As for the MOSFET.. just use whatever you got at this moment, to get it to work. After there, you can optimize. But my guess is, that the MOSFET youre using now, will dissipate around 5W.

Are you using any constant-current curcuit? If so, you need to protect it somehow. Cause if the temperature of the MOSFET rises, the CC-circuit will step it up a notch, and the temperature of the MOSFET will rise even more (higher temp. = higher resistance) - and you will have a thermal runaway (and smoke).

EDIT: Found something that could help you: http://books.google.com/books?id=R8...v=onepage&q=hall effect mosfet switch&f=false

Here they use a 12V-zener diode. Give it a look. Tho it doesnt change that its reversed..

 

[gt40]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

As far as the HE sensor goes, its active low. This means that the output is inverted of what you would normally experience (normally its: on = high. But not here).

Solution is either a P-channel MOSFET, or a N-channel and an inverting gate driver - such as the TC4426.

As for the MOSFET.. just use whatever you got at this moment, to get it to work. After there, you can optimize. But my guess is, that the MOSFET youre using now, will dissipate around 5W.

Are you using any constant-current curcuit? If so, you need to protect it somehow. Cause if the temperature of the MOSFET rises, the CC-circuit will step it up a notch, and the temperature of the MOSFET will rise even more (higher temp. = higher resistance) - and you will have a thermal runaway (and smoke).

EDIT: Found something that could help you: http://books.google.com/books?id=R8VAjMitH1QC&pg=PA96&lpg=PA96&dq=hall+effect+mosfet+switch&source=bl&ots=XuPREiEq8u&sig=SwK65H9KtGoq919rtm-jrC2bpLE&hl=da&ei=E808TLuZKIX_OZa5yfgO&sa=X&oi=book_result&ct=result&resnum=7&ved=0CDsQ6AEwBg#v=onepage&q=hall%20effect%20mosfet%20switch&f=false

Here they use a 12V-zener diode. Give it a look. Tho it doesnt change that its reversed..

I am still unclear here. If I understand right, I need the following:

1. P channel mosfet that can handle 12 amp range and has really low ron.
2. Hall sensor that is active low
3. not sure on on anything else and suggested parts would be awesome.

In the meanwhile, I am proceeding ahead and made a second heatsink using the irz34 and reed switch with an embedded copper core running all the way through. Here are a few pics so far:

IRZ34 ready to be embedded in the heatsink:

Installed and ready to be soldered:

Another shot of the rear. I am going to face and bore this out and install a black delrin sleeve and copper contact plate in the center:

Hope to cut the channel for the reed switch and wire it up tomorrow per the diagram I posted in the thread.

This heat sink will eventually have an LDO10C Driver put in like my mag 3c so I can add a longer tube and run (2) 26650 imr batteries at a full 9+ amps

 

[MikeAusC]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

As far as hall effect sensors, I have some of these: http://media.digikey.com/pdf/Data%20Sheets/Infineon%20PDFs/TLE4905L,%2006L,%2045L,%2045-2L.pdf

The 4905L's. Would this work?

Think of these as a switch which connects the Output to the -ve terminal when it detects a magnetic field. Because it's a semiconductor, you can't rewire it to switch to +ve to drive the gate of an N-channel FET.

So connect the Output to a 10k resistor, connect the other end to the Base of a PNP transistor. Connect the transistors Emitter to +ve. Connect another 10k resistor between the Base and Emitter of this transistor.

Connect the Collector to a 100k Resistor and to the Gate of your N-channel FET. Connect the other and of the Resistor to -ve to ensure the FET is switched off when the PNP Transistor is off.

 

[gt40]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

Think of these as a switch which connects the Output to the -ve terminal when it detects a magnetic field. Because it's a semiconductor, you can't rewire it to switch to +ve to drive the gate of an N-channel FET.

So connect the Output to a 10k resistor, connect the other end to the Base of a PNP transistor. Connect the transistors Emitter to +ve. Connect another 10k resistor between the Base and Emitter of this transistor.

Connect the Collector to a 100k Resistor and to the Gate of your N-channel FET. Connect the other and of the Resistor to -ve to ensure the FET is switched off when the PNP Transistor is off.

Thank you for clarifying things a bit. FYI, i found the hall sensor data sheet on the one that actually worked with the tip107 darlington transister: http://www.allegromicro.com/en/Products/Part_Numbers/1321/1321.pdf

 

[MikeAusC]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

FYI, i found the hall sensor data sheet on the one that actually worked with the tip107 darlington transister: http://www.allegromicro.com/en/Products/Part_Numbers/1321/1321.pdf

This is a Linear Hall Sensor, not a switch.

The output will vary between -ve and +ve depending on the stregth and direction of the Magnetic field. It could drive an N-channel FET directly, BUT . . . .

The danger when using this to drive a FET or Bipolar transistor is that it may partially turn on the transistor, causing very high dissipation. OK, if the system is designed to work that way, but can overheat the transistor otherwise. Worst case is that the transistor will dissipate the same amount of power as the LED - a simple dimmer, but a very ineffcient one.

EDIT - With no magnet nearby, the output will be halfway between +ve and -ve, which makes it hard to drive a switch. If you place a small Magnet near the sensor it can bias the sensor to go to +ve or -ve. Then the switch contains a stronger magnet of the opposite polarity that drives the output to the other extreme.

 

[gt40]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

This is a Linear Hall Sensor, not a switch.

The output will vary between -ve and +ve depending on the stregth and direction of the Magnetic field. It could drive an N-channel FET directly, BUT . . . .

The danger when using this to drive a FET or Bipolar transistor is that it may partially turn on the transistor, causing very high dissipation. OK, if the system is designed to work that way, but can overheat the transistor otherwise. Worst case is that the transistor will dissipate the same amount of power as the LED - a simple dimmer, but a very ineffcient one.

EDIT - With no magnet nearby, the output will be halfway between +ve and -ve, which makes it hard to drive a switch. If you place a small Magnet near the sensor it can bias the sensor to go to +ve or -ve. Then the switch contains a stronger magnet of the opposite polarity that drives the output to the other extreme.

I was wrong on the hall sensor spec sheet. I looked it up based upon the markings on the pic. The place I bought it finally gave up the correct sheet:

http://www.melexis.com/prodfiles/0004824_US5881_rev007.pdf

This is the one that worked with the darlington transister. Could I use it with a p channel in the same way?

Also, I found an example on this hall applications guide that seems to do exactly what I want. The example makes a 50v/50 amp switch with a hall effect sensor and power fet. It is on page 33: http://www.melexis.com/Assets/Hall_Applications_Guide__3715.aspx

Not sure which type of hall sensor or fet they are using though. I e-mailed Melexis and will see if they respond.

One more question, could i use the 5881 hall effect sensor to switch on a p channel like this one:

http://www.irf.com/product-info/datasheets/data/irf4905.pdf

Thanks btw for responding to my newbie questions:thumbsup:

 

[MikeAusC]

Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin

This is the one that worked with the darlington transister. Could I use it with a p channel in the same way?

This one switches output to ground when it detects a magnet - so it can drive a P-channel FET directly or N-channel via a PNP transistor.

If it's possible to have the LED on when the magnet is AWAY from the sensor (or use the bias magnet mentioned above), then you can drive an N-channel directly.

But are you aware the Hall Switch will draw 2.5mAmp from the battery continuously ?

Also, I found an example on this hall applications guide that seems to do exactly what I want. The example makes a 50v/50 amp switch with a hall effect sensor and power fet. It is on page 33: http://www.melexis.com/Assets/Hall_Applications_Guide__3715.aspx

Not sure which type of hall sensor or fet they are using though. I e-mailed Melexis and will see if they respond.

This is a conceptual diagram if it shows no part numbers - the FET will be OFF when the magnet is near the sensor (or use the bias magnet mentioned above).

 

[MikeAusC]

Re: compact sst90 aspheric waterproof light build log

I really think you need to use a Reed Switch instead of a Hall Switch to avoid the continuous 2.5mAmp drain on the battery when the LED is off.

Connect the Reed Switch between +ve and the Gate and connect a 10k resistor from Gate to -ve.