Hi

I am new here, but I tried the search and didn't find what I am looking for.

My goal is to make circuit which will calculate my golf club swing speed. Maybe more features later.

Idea was to make a circuit with 2 sensors 5cm apart connected to comparators which are connected to pic microcontroller ports. And pic is counting time between those 2 pulses. I think sensors could be phototransistors or diodes. I want that circuit(pic) to be able to count 1-10uS time between pulses.

I have tested this comparator circuit found in attachment. But how do I add some hysteresis and gain control for different light situations.

For gain control I tested this circuit by replacing voltage divider with samekind of phototransistor and resistors. It worked, but when I added 100k hysteresis it gave me noise on output. Comparator input voltages were 0.2-0.3volts

Any comments about whole idea are welcome, also different ideas how this could be implemented.

Masa

 

I've done similar things in the past, including using a gyrosensor on the club itself.

But I found this idea that I think could do it:

http://electronicdesign.com/Articles/Index.cfm?ArticleID=3597

good luck

 

Consider using a couple of fixed laser pointers aimed at the phototransistors, (which would be shielded from ambient light) to create two precise beams which would then be interrupted by the club.

 

Hi

Thanks for fast answers, actually I was thinking about pointing those sensors up from ground together with one led or irled. And when club head crosses this led + sensor, it will reflect some of the led light back to sensor. Also I need to connect this to microcontroller which will be able to do some other stuff and maybe I will add few more of those sensors.

I took some time with reading that link you posted, I am not sure if I understood that correctly. I just don't like using circuits that I don't fully understand how those works. Maybe I could take that sensor part and and connect those comparators to my pic.

But is it not possible to make it this way I have described it.
2 optical sensors paired with leds, all pointing upward.
And when object crosses first sensor + led some of the light is reflected back to sensor. then comparator will give steady +5v to pic and pic will start counting. And when club reaches second sensor it will stop counting.

Reason why ambient light cannot be used is that I am planning on adding more sensors which will calculate the angle of club. And club head is not square so I need to add some square reflective tape on bottom of club head. That is the reason why I need leds pointing upward

Masa

Masa