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Introduction and explanation for help on a circuit...

kubricky

Dec 9, 2009
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Hey folks, I have been searching these electronics forums and have asked questions on another but found a great deal of scuttlbutt. This one seems the most BS free and as I am stumbling head first (back) into trying to understand electronics and building little things I definitely need some guidance. I recently completed my first project in more than twenty years -- I converted a cheap driveway motion sensor (battery operated) system to switch on a 110v power strip for a set amount of time (1M pot, 555, a relay, some capacitors and resistors). I still need some help with placement of diodes, but I am working it...smoke-tests.

I did that so that I can start plowing into an idea I have for my hobby of road racing motorcycles. I am certainly no pro, but I enjoy doing it and have an interesting idea that requires a little thought but more so it requires the most efficient electronic components. I believe ultimately this idea could benefit the amatuer road racer and intermediate to advanced track-day rider.

Basically, I would like to use a laser diode or LED Tx/Rx set (which has the highest "resolution", ie., can read the most breaks to the beam in 1 (one second), I understnd that there is a chipset already built that can do this but don't understand the theory behind the chip as it appears the chip only gives the signal to a Tx and would require a Rx. Ultimately two of these will be used.

I'd then like to feed these signals into a componet and "sync" them the resulting out put being a baseline that does not change if there is a change in rate across both but only if there is a change across one. I am sure you have a lightbulb going off as I am trying to describe this as I have been told there is an Op-Amp or Opto-Comparator which can do this. I am told I will also need an Opto-Isolator to clean the signals.

Ultimately I am looking to trigger something for user-selectable amount of time (i.e., the 555 and mini-pot) from .5 to 2.5 seconds.

On the trigger side, I will use normally closed relays and the trigger will close them. I would like to feed the single tigger component into a ciruit which will "amplify" the trigger signal over 4 outputs and randomize it going to each of these outputs.

I know this sounds like a lot, but I am hoping not to have to incorporate programming and keep it extremely simple. Can anyone help???
 

Resqueline

Jul 31, 2009
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Welcome to the forum.

You are explaining a lot but still being vague about your goal, and it leaves a lot of questions.
Please be more specific about what you have to work with and what you want to achieve, and leave the other ideas alone for now. Are you after a frequency comparator (like for gear speeds)? What speeds and resolutions are we talking about?
And revealing the final purpose of the project can only bring about a quicker conclusion.
Closing normally closed contacts is a contradictory expression.
4 randomized outputs sounds like a job for a 2-bit counter (+ some extras).
Amplify; what currents and voltages will be needed for the outputs?
 

kubricky

Dec 9, 2009
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Dec 9, 2009
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Thanks a bunch for the reply. First of all my mistake on closing the normally closed relays. First of all the system will use normally closed relays and the trigger will OPEN the normally closed relays.

I am trying to put together a traction control that does not require true signal processing or a PIC. Can I call this solid state? I do not want to program an eprom or rom chip to complete computations/calculations (they may not call them eproms any longer, actually I believe it is a PIC - programmable IC).

Functionally I would like to detect the difference (delta) in wheel speed between two wheels and when there is a change activate a relay (to open) for a very short amount of time to turn off ignition coils. This is the basic principle behind traction control without historical data and signal processing from a host of other typical DAQ (data acquisition points). I would like to be able to vary the relays (always two at a time) with a pot and rc network for time (.2 to 1 sec) as well as randomize how they turn off so the same ignition coil is not always used.

I believe I can use a phototransistor to get a signal from the 670nM laser diodes found in a cd rom drive affixed to the front fork and rear swingarm to using the existing holes in the rotors for the "wheel speed". Can I then use an op-amp as a comparator to take the positive output from each "wheel speed" sensor and bring them (AT ANY GIVEN TIME) to 0? Assuming yes, I would then say that a + or - voltage on this circuit would indicate a difference in wheel spin (i.e. loss of traction) and then use a circuit to OPEN relays which are inline with ignition coils. I will use a 555 (I see a number of folks advising to stay away from the 555 for timing -- why is this?) to build a small timer circuit to connect to the rear brake which will bypass the system. The rear brake is sometimes used (in roadracing and often in dirt) to break the rear loose so because the stop or slowing of the rear should register a difference in wheel speed, I want to be able to bypass the system. Additionally sometimes the front wheel is off the ground and sometimes (not often!) the rear wheel is off the ground and I will use accelerometers in the circuit to turn it off for a moment if/when this happens.
 

Resqueline

Jul 31, 2009
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Ok.
First you'll run into dirt problems using optical devices on bike wheels. In such environments magnetic reluctance pickups are used.
Anything w/o vacuum tubes is called solid state.
Then you use frequency-to-voltage converters. Comparing these two outputs with an op-amp will directly give you the wheelspin. If the op-amp output goes "negative" it indicates rear wheel braking and thus this signal can simply be ignored, so you don't need a brake signal & timer.
A "positive" output can be fed to a flip-flop that alternates between the two (coil) outputs.
 

kubricky

Dec 9, 2009
3
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Dec 9, 2009
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Ok.
First you'll run into dirt problems using optical devices on bike wheels. In such environments magnetic reluctance pickups are used.

In this case, I'd ask how much the dirt will affect the system? Will the affect be realized by lap, by session, or by day on the racetrack? More specifically, is it particle matter or big spatter and rain drops, etc.? I ask because asking people to affix a point to the wheel as a pickup can be disastrous. Even minor variations (assume 1/4 oz wheel weights) need to be accounted for in balancing, additionally, it may be harder to keep the magnet on the wheel if it isn't on the outside of the rim, with the centrifugal force trying to dislodge it).

Ok.
Anything w/o vacuum tubes is called solid state.

So, this is solid state, but what I mean to say is without true signal processing -- thanks.

Then you use frequency-to-voltage converters. Comparing these two outputs with an op-amp will directly give you the wheelspin. If the op-amp output goes "negative" it indicates rear wheel braking and thus this signal can simply be ignored, so you don't need a brake signal & timer.

I am still looking to use the rear wheel spin to "trigger" the system. In many cases the rear wheel is intentionally spun up or the wheel is locked to begin "sliding into" the corner. In that case I'd use the rear brake lever to activate a switch and a 555 as the timer to effectively "shutdown" the system for a up to 1 second. Rear wheel speed and slip would be monitored because many low sides are caused by too much gas to the rear wheel which starts a spin and just carries, in these cases, I'd like to have that difference "trigger" the relay(s).

A "positive" output can be fed to a flip-flop that alternates between the two (coil) outputs.

So I would do this as well with a negative output as in a rear wheel spin/slip/slide.

Much obliged for your help. You seem to be the guru on here and I'm sorry to take your time but I do appreciate the help. Any thoughts on a simple magnetic system to use to get the first version underway (I could redesign later with optics) and as I will test it, I will chack wheel balance). If you can provide a few thoughts, I'd like to draft a quick schematic to use on the workbench and have you review for accuracy is you wouldn't mind.

Thanks again.
 

Resqueline

Jul 31, 2009
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There's no need for magnets on the wheel. Look up magnetic reluctance sensor and you'll find it is a small coil incorporating a magnet. It needs to be in close proximity to the rotor and needs an extra amplifier but will then detect the holes even easier than optics.

Optics are easily compromised by a single speck of dirt or a drop of water. On a dirt track this is likely to happen within seconds. Even if specially designed for dirt tolerance I wouldn't expect it to last a lap.

It's ok, as long as the communication is good, I do this because I enjoy helping people. Colleagues at work also always ask me about this & that because I seem to know "everything"..
I'll review the circuit for you when you get it "on paper".
 
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