[TTmartin]

I've started connecting up my soliton 1 controller.
Just finished making the rpm sensor pick up.

The two 8mm bolts are screwed into the collar and drill dimpled into motor shaft, also loctited with stud lock. the two bolts create a 120mm diameter.
The switch I have used is a siemens 10-30v dc pnp 6mm field, Bero 3rg 4612-0ag01. my question is, will this switch be ok with the soliton 1 or would a 2mm field be better, also for a (non electronics) mere mortal like me could someone explain what the pulldown or pullup (depending on pnp or npn) resistor does? is this resistor built into some switch types, as I work with these switch types alot in the industry I'm in, but no extra resistors are involved.
If I'm asking a stupid question then sorry in advance, I would prefer to understand what I am actually doing

[ruckus]

My understanding of 'pull down' vs 'pull up' is that it is really the same as saying normally open or normally closed. A pull down is taking a steady signal and cutting it for a split second as the bolt goes by. A pull up is normally dead but sends out a pulse signal as the bolt goes by. I could be wrong.

I don't think 1mm vs. 2mm matters, as long as you get a consistent signal. Obviously, the 2mm gives you a bit more room for error. Does your inductive proximity sensor have a little light on the back? I like that kind because you can see that it is working and it helps with adjustment.

I tried a bolt sensor (with much shorter bolts!) with the Zilla but it was really picky and needed a full 50% duty cycle (half metal, half air) so I had to buy a special reluctor ring from rechargecar. It works great.

Good luck.

[skooler]

Loads of good informaton in this thread

http://www.diyelectriccar.com/forums...ad.php?t=71903

Theres also a nice picture of my pullup resistor on the soliton.

My understanding is that a pullup resister increases the voltage - which increases the voltage of each pulse making it easier for the controller to recognise.

Hope this helps.

Cheers,

Mike

[TTmartin]

:

Originally Posted by skooler

Loads of good informaton in this thread

http://www.diyelectriccar.com/forums...ad.php?t=71903

Theres also a nice picture of my pullup resistor on the soliton.

My understanding is that a pullup resister increases the voltage - which increases the voltage of each pulse making it easier for the controller to recognise.

Hope this helps.

Cheers,

Mike

Thanks Mike,
But all that maths is a bit beyond me
so is my 120 diameter rpm pickup with 13mm wide sensing bolt heads x 2 going to do the job?My plan was to see what it does compared to a rpm tester that I can borrow from work.

I've just spent 30 minutes on the big wide web, looking for explanations for pull up and pulldown resistors used with proximity switches, just so I might understand a small fraction of the magical world of (electricery). I should be on the patio drinking beer, we have some sun for a change

It seems to go like this,
if using a PNP proximity switch for a task like an rpm
sensor you don't want any stray voltage/interference/noise, to upset the signals, so you wire a resistor from the signal connection to ground (pulldown) this ensures any unwanted (noise?) Goes to ground giving crisp clean on off switching to give accurate rpm sensing.
If using a NPN proximity switch it's the opposite you wire a resistor from the signal connection to +V (pull-up).
I think I've got it? Now wheres that beer?
If that explanation is wrong, some one please let me know

[TigerNut]

@TTMartin: Correct. A pull-up or pull-down resistor provides a conductive path when the switch that it's tied to is open-circuit. Otherwise the input line will float to whatever voltage it wants... not what you want.

@ruckus, skooler: Not correct. You need a pullup or pulldown resistor with both NO and NC switches; the only case that's not true is if you have a double-throw switch, with one side wired to (say) 12V, the other side to ground, the common to your signal input, and the switch is guaranteed to be break-before-make. In that case, though, it may exhibit 'bounce' in the brief interval that nothing is connected to the (common) input.

For maximum interference suppression, you want the pullup or pulldown resistor to be as low as possible bearing in mind that when the switch is closed, you'll draw a corresponding amount of current, and if the switch is a PNP or NPN transistor, it has a maximum current limit. The power rating of the resistor is also worth considering, if the duty cycle of the switch is at all significant.

[MalcolmB]

Hi TT

There's no need to use such long bolts. The aim is just to produce two pulses for each rotation. You could make the bolts much shorter and move the sensor closer to the shaft to reduce the risk of unbalancing your motor. If the heads of the bolts are closer to the shaft it will also increase the duration of the pulse, which will make it easier for the controller to 'see' the pulses.

Here's a pic of my setup.

[TTmartin]

Originally Posted by MalcolmB

Hi TT

There's no need to use such long bolts. The aim is just to produce two pulses for each rotation. You could make the bolts much shorter and move the sensor closer to the shaft to reduce the risk of unbalancing your motor. If the heads of the bolts are closer to the shaft it will also increase the duration of the pulse, which will make it easier for the controller to 'see' the pulses.

Here's a pic of my setup.

Thanks for the input,
The two bolts are accurately drilled & tapped into collar aposing each other and are of equal length so I think balance of motor should be fine.
The reason I made the set up with bolts of this length was to create a big enough diameter so the soliton 1 controller can actually count the pulses at high rpm to give an accurate reading. As I understand it, the smaller the diameter the faster the controller has to read the switching and I think there is limit.
I happened to read this description from another thread about rpm sensors, See-below,

[quote]
Finally, the Soliton controllers need the pulses from the tach sensor to be at least 200us wide (whether starting from ~12V and dropping to 0V when the target approaches or vice versa) or the hardware filter/squaring circuit will ignore them. In other words, the sensor targets need to be a certain minimum width relative to the circumference of the circle they scribe as they rotate. For example, let's say you want to read up to 7200 rpm so you can effectively limit the motor to 6000 rpm (the controller needs to be able to read a higher rpm than the desired limit). If you make a disc out of aluminum and cut two notches in it for an inductive prox to sense, the notches need to be at least 1cm wide if the disc is 12cm in diameter.

The math behind this is straightforward: the linear velocity on the surface of the disc is pi*d then multiply by RPM, divide by 60 to get the surface speed in cm (or inches) per second. Divide the width of the sensing target in cm (or inches) by the surface speed and the distance component cancels out, leaving you with the pulse width in seconds. Multiply that number by 10^3 to convert to milliseconds, or by 10^6 to convert to microseconds. The resulting pulse width must be comfortably larger than 200us at the highest RPM to be read.[quote]

I made my set up based on what I understood the above to mean.
Have I got it wrong?

[MalcolmB]

Originally Posted by TTmartin

Have I got it wrong?

No, you haven't got it wrong, you've just met the minimum requirement. As you move the bolt head closer to the shaft you increase the time it takes for the head of the bolt to pass the sensor. It might be easier to picture if you think of slices of pie, drawn from the centre of the shaft to the outer edges of a bolt head. The slices get fatter as you move the bolt head closer to the shaft. The fatter the slice, the easier it is to 'see'.

[TTmartin]

Originally Posted by MalcolmB

No, you haven't got it wrong, you've just met the minimum requirement. As you move the bolt head closer to the shaft you increase the time it takes for the head of the bolt to pass the sensor. It might be easier to picture if you think of slices of pie, drawn from the centre of the shaft to the outer edges of a bolt head. The slices get fatter as you move the bolt head closer to the shaft. The fatter the slice, the easier it is to 'see'.

I think I'm missing something here,
As I see it the larger the diameter, the longer between switch signals making it more possible for the controller to be able to count the switch pulses at high rpm.
If you make the diameter two small it would eventually become one continuous signal to a controller at high rpm, at some point before that state you will receive inaccurate data, at low rpm its not an issue.
At the end of the day I suppose the best way to monitor whether an rpm sensor set up is working accurately is to use a hand held tacho-meter,
Luckily I am able get my hands on a rpm tester.

[ruckus]

Originally Posted by TTmartin

I think I'm missing something here,
As I see it the larger the diameter, the longer between switch signals making it more possible for the controller to be able to count the switch pulses at high rpm.

Here is long-bolt rpm sensor result:
----------^----------^----------^----------^----------^
Here is short-bolt rpm sensor result:
-----^-----^-----^-----^-----^-----^-----^-----^-----^

Which has better resolution and accuracy? At low rpm your tach needle will go THump Thump Thump. It won't be smooth.

We are talking about electronics here. They can handle very high frequencies with no problem. Creating a low-frequency tach output is not necessary or desirable.

I would shorten the bolts as much as possible.

Either way should work though... It is merely a matter of aesthetic and accuracy.

Here is the Tach sensor on the 37 Jaguar:

This is fresh install before the wire was secured...