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Frequency "averager"

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Greetings, all

I am looking for a means to get the average of two frequencies.

At first I thought a simple adder circuit would work, but I realised that I will get complex waveforms, or even a zero value when the two frequencies are the same but phase-shifted 180°.

I don't care about the amplitude, as that is restricted by the pickups. I also think the signal could be either sinusoidal or square. The output should be the average of the two frequencies, and of either the same or the average of the two input waveforms.

Thank you
 

alec_t

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Sounds like a job for a micro plus a digital synthesiser. I think it would be convoluted to do it any other way.
 
My car was designed for, but not equipped with, ABS. I am considering my options to install ABS on my car.

The ABS my car was designed for, was a 3-channel system. It had one sensor for each front wheel, and a sensor on the input shaft of the differential for the two rear wheels. To purchase all the hardware is relatively easy and cheap, except for the differential which can accommodate the 3rd sensor - even 2nd hand, that would cost more than the car itself. So I was thinking about installing a later 4-channel system, which would not invade the existing hardware.

But then I got to thinking that all I really need to do is to substitute the diff sensor with the average signal from the two rear wheel sensors, and I can use the original ABS system. Installing two reluctor rings on the rear half shafts and two sensors and brackets is easy, which is why I considered a 4-channel system to begin with. Then I wouldn't have to adapt any different ABS regulator, ABS ECU etc - it would be a straight install of the original equipment.
 

alec_t

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Have you checked with your insurer that a home-brew mod of this sort wouldn't invalidate your insurance? There are serious safety issues here.
 

shortbus=

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But then I got to thinking that all I really need to do is to substitute the diff sensor with the average signal from the two rear wheel sensors, and I can use the original ABS system. Installing two reluctor rings on the rear half shafts and two sensors and brackets is easy, which is why I considered a 4-channel system to begin with. Then I wouldn't have to adapt any different ABS regulator, ABS ECU etc - it would be a straight install of the original equipment.

If your capable of making reluctor rings and pickup mounts for the half shafts, why not just add a single reluctor ring and pickup to the differential input yoke? Or get an OEM ABS yoke that has the reluctor ring? The yokes are made to come off of the pinion so only changing or modifying a yoke should be easy.
 
I am not capable of making reluctor rings. Luckily I am able to purchase reluctor rings that fit the drive shafts and have the same number of teeth as the front reluctor discs.

Different differential ratios had different numbers of teeth on the input shaft to compensate for the final drive ratio. Why not just compare wheels speeds with wheel speeds?
 

shortbus=

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Why not just compare wheels speeds with wheel speeds?

Then why not use the ABS made to go with that type vehicle? I really have to agree with Alec_T. Someone not understanding electronics is probably a accident in the making when doing something like this. In the event of an accident if it was found that there was a cobbled together system, whether the brakes were involved or not, you could loose everything you own and a lot of what you will earn for the rest of your life. Is ABS worth it?
 

dr pepper

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A Pll might do the job, but it would take some electronics knowledge and a lot of fiddling, plus as alec says its not something you want to cobble together for a brake system.
I've messed with vehicle electronics a fair bit but never come across a single abs sensor for the rear wheels, sounds like something bmw would do.
Might be better to go for the 4 wheel system and leave it as unmodded as possible.
The abs system has parameters for the vehciles dynamics such as vehicle sprung and unsprungweight, suspension properties, tyres etc, if you take an abs controller off a diffrent model, even the same bodyshape it may not necessarily work as intended, the car would have to have the same engine, suspension, curb weight, tyres&rims etc.
I found all this out when I converted a classic mini to 2.0 rover power, I was going to fit the rover's abs system, however with this knowledge decided it wasnt a good idea.
 
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dr pepper

Well-Known Member
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I spose if both rear brakes are on the same circuit it'll work just fine.
 
Here is a typical 3-channel, 3 sensor ABS system from the 80's through to the late 90's

US08239109-20120807-D00001.png


Here is a more modern, 4-channel ABS with 4 wheel sensors:

ABS-architecture.png





Here is how I hoped to adopt ABS to my car - a 3-channel, 4 sensor ABS system:
1.jpg
 
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