Hall effect sensor tester

[Leslie]

13.55 @ 1 amp.

The Lm317t sink needs to be a little bigger as its getting hot to touch.  As the voltage gets higher on the battery this wasted wattage should lower by about 2 watts.

The transfromer is warm to touch,

We can do some Lm317t heatsink calculations tomorrow to pick the best option for a heat sink.

This would be perfect 1 amp constant current charging station for test charging 4 Lifepo4 cells.

[Leslie]

Finished charging the 24ah SLA. from 12.55v cold to 15v hot.

Holding 15.00v and still a rock solid 1 amp.

[Leslie]

Ok I want to make this more efficient.  We are loosing a lot of wattage in the initial stages of the charge.

But we can start working on our hall effect etser and stuff now.

Im am going to use another linear regulator called an LM7805 or if I regulate the voltage closer to 5v with a resistor A LM78L05 Should be fine.

http://www.national.com/ds/LM/LM78L05.pdf





As you can see the regulator is very simple and easy to configure for the power supply.

I will offer up a better circuit design pics soon.

I am going to try can use the ground referance point on three of these LM78l05 to to switch the leds off and on.

The ground pin requires smaller than 10ma to regulate a 5v signal so we can kno we are not overloading the hall sensors to run the leds..

[Leslie]

Here is a preview of the newer circuit, I need to test out.

Maybe stick some 100 ohm variable pot resitors on the hall output wires to calibrate the off voltage to 0v.  We will see soon.



This should be able to run forever off the halls and create very little load on the hall sensors.

The lights will switch on when ahll sensor is on. and the LM7805 should not need to draw any huge am,ount of current to switch on.

I need to learn how much current actually negates the led to switch off.

The power supply.


The circuit provides 9v to the entire circuit, the hall senors are rated 5v @ 7ma.

We are running three sensors so we will need to burn off 4v @ .021 amps.

9v @ .021a Circuit = 428 ohms.

We can not exceed 428 ohms in this sub circuit.

3 hall sensors in parallel rated at 5v draws .021 amps

hall R= 5v/.021a = 238 ohm

Calculate the divider.

428 ohms - 138 ohms = 290 ohms.

290 ohm 1/4 watt for load regulation to the hall sensor.

The lamps..


With 140 ohm resitor when the hall supply is opend through the output on the ground pin it provides 3.8v to this ground pin causing the the output volats of the lm780-5 to swing + 5v to 3.8v 8.8v

The 140 ohm resistor needs to be enough to allow 50ma of cirrent through at 8.8v.  So 136 ohm is perfect

When the hall sensor closes to ground 0v it causes the ground to regulate the LM78L05 to 5v and the resistance of the whole circiut should be 180 ohms at 5v.  And should only allow .027 amps to flow this led should drop to almost on at 1.1v and switch off.

The load of the leds should have no effect on the input of the hall in anmy case there is no reason you can not filter it
..

So we put this circuit away and play with it soon and work on a throttle tester as I wait for some funds to get the regulators and test this out.

[Leslie]

I just bought some parts to build this circuit.

I just lost the parts to build this circiut.

 




The smallest Led I could get was in the 20ma range which is the absolut max that a hall can pass.

I still think for a lab tester I don't want to be stressing the parts inside the motor.  Because of how much work the halls take to replace.

Im still going with the regulator ground pins to do my switching.


Here it is simulated as best as I could manage.

[Cornelius]

Why not just use some driver transistors triggered by the hall sensors to drive the leds? Then you can skip the 7809 and the resistor, and use only one 78L05. (which are rated for 100mA; enough for all 3 leds...)

[Leslie]

The LM7805 uses a reference voltage to regulate the volatge.

I am using the ground pin and it only needs if that 10ma,  I think the transitors unless they are Fet have to use too much resistance on the base to switch it on.

Can you suggest a part that can switch a 5v 20ma source from the base to emitter with under 10ma base current?  no fets as this may require a biase.

Oh I get it,

Maybe I could get the voltage to 2.5 v as far as the transistor can go down in volts and have it almost on at the base. Then whe the hall fires some current it opens the BCE to open and we have a light.

Correct?

[Leslie]

Like this.

[Leslie]

The MPSA13 looks like it will work,



I found this very simple IR detector circuit that almost looks the part.

Will this transistor do the trick?

[Leslie]

Ok I got this MPSA14 transistor going.  Its pretty sensitive with A ^hFE of 5000 at 5v 10ma



Originally I want this circuit to run installed on the bike too.  I can see this happening still.

Base on voltage meets our requirements @ 2v nd this darlington pair transitor has a hair trigger,

I can get it to switch on at 2v 2ma.

I have got all the current going around the circuit pretty efficiently.  It a little hot up the top but you need to cut some watts out somewhere.

Now to draw it up,

I am pretty sure my last circuit using the LM7805s for amplifiers worked in my humble opinion.  But I will conceed this design is better again.

If you look the led is drawing 2v @ 20ma the base to trigger is only 2.5ma and is set at 2v,

You can save a heap of base current placing a resistor beteen gnd and emitter .

The switch simulates the hall switching at the base leg causing the transitor to switch on and off.

[Leslie]

Here is the 5v version.

[Cornelius]

Seems like you're on the right track here... Most general purpose small signal transistors can deliver around 100mA and they only need 0,7V to open the CE...

Now, I haven't practiced this theory since school 20-25 years back, so it's only form memory my suggestion...

[Leslie]

Seems like you're on the right track here... Most general purpose small signal transistors can deliver around 100mA and they only need 0,7V to open the CE...

Now, I haven't practiced this theory since school 20-25 years back, so it's only form memory my suggestion...

Same here I did electronics engineering 25 years ago and didnt even use any of it till I got an ebike.

The simulation proggy helps a lot.

I wanted something that had low volts and current on the base and the simulation transistor seemed to started switching on at .7 and full on properly between 1.8v and 2v just like the spec sheet says.

I saw one circuit with darlington pairs trigger from the current off you fingers.  EG touch sensitive..  I got a grip on the math for the transistors but I need to familiarise myself with how it works or else I am wasting my time.


If you were to ask me ohms law, LOL I couldnt tell you, I have to look at each calculation I am making and make it up.  The Law helps you to understand how the processes of the math works in the science. But if the penny doesnt drop, attempting to apply the math is a trivial pursuit.  If I wasnt to understand how it works I woukldnt even know what Law goes where.

Its 2am here and I am getting tired.  More of this latter,

Thanks for the suggestions.  I am determined to make this proper

Sooner or later I would have to deal with the transistor formula again.  I was trying to avoid it.

I am waiting to get the bills together for a Magic Pie and just building things while I wait.

I will be looking at building a BMS for some cells I have comming and using that 1 amp transformers ive been playing with..

Again I was going to use the LM338 almost identical to the LM317t but 5a rateing for each cell but this is overkill compared to some small transistors.  But the current and voltage regulation on a cell would be spot on.

I had a simulation BMS built just using resistors and its fine at 1 amp.  Something about using 10% of your charge for balancing.

Last but not least I have some LM2576 simple switchers ICs good for 60v I am itching to put right up at the rectifier. And on a solar panel charger I am working on.

The four panels in series reads over 80v and can output 80 watts at 68v and I plan to use 18 lifepo4  cells on the trailer jump battery.  59.4v cold and 64.4v hot. And for my main bike pack I want 16 cells.

The solar jump pack will be a 1.2 amp charger to the other pack.  This will allow the current always travel down hill to my bike pack.

Anyway thanks again.

Good night all.  I needs some sleep.

[Cornelius]

If you're looking for efficient voltage regulators, take a look at the MC34063... It exist in most car mobile phone chargers and can handle up to 1.5A by itself. It's a dc-dc converter in an dip-8 package, and can regulate both up and down...
Who hasn't some 12V mobile phone chargers laying around?

http://www.st.com/stonline/products/literature/ds/5257/mc34063eb.pdf

[Leslie]

That 8 pin pack would be great as a sub circuit switcher.