Electronics > Projects, Designs, and Technical Stuff

lm339 and bit of fun with accelerometer

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Greg J:
I am preparing bits for my robot, and one of the things I wanted to toy with is robot drive, and accelerometers.
I am software engineer (I know, booooo), but I started as a young electronics guy. So I like to develop electronic bits the same way I approach software.
In small, manageable bits that I can test, and toy with - before putting together full design.

Here's a simple schematic of one of the parts, the idea is that if the probed voltage is below half point, one LED will be on, otherwise second one will be on.
This will then drive H motor driver, and will see if it will work.

Here's the schematic of it:

Anywaaise, here's video

Please let me know what you think, throw any comments - common sense applies of course.
But I am very interested to know what you think. Like I said, I'm software guy by day - wanna learn more about electronics by evenings.

Greg J:
playing with it some more, I've added h-bridge with engine like so:

This is suppose to be driven by where LEDs are in my LM339 schematic. But it only works for the first LED, the second one doesn't drive anything.

Where did I go wrong, and how can I fix that? Any ideas please ?

Greg J:
Thanks for the massive amount of help! Really helpful this silence , no kidding !

I've managed to get it working. Now it just drives h-bridge.
But it turned out my drive does;'t have the torque to drive the robot and keep it balanced. Doh ! Someone shoot me please, for not thinking about it.
See it yourself, pretty pathetic !

Also, now I think I'll need to oompff the power on this thing, proper dc motor with some gearbox that'll have enough torque is 12V , I think (correct me if I'm wrong of course).
Here's new schematic for the complete thing (without accelerator, but you get the idea).

Again, comments are welcomed. Seriously!


--- Quote from: Greg J on December 25, 2011, 09:36:07 pm ---Thanks for the massive amount of help! Really helpful this silence , no kidding !

--- End quote ---

It's Christmas. I for one am busy with family, sauna and beer.

Why is Q1 not a BC547 as well?
I would place a pull-down resistor at the non-inverting input of IC3.

Greg J:
Because I didn't have another one around ;) I used whatever I had in drawers, and whatever maplin had in stock.  (and they are usually having 1-2 transistors of each type, if any, absolute joke!)

Now, I might actually ditch that transistor all together and just end up using two 741. Because the idea is to have H-bridge drive motor one or the other way depending on the input voltage. When its below 1/2 Vcc, one way, above - the other way. Will it work? is a different matter, but I'll save quite few transistors if that's the case.

Since my motor turned out to be crap, I want to try 2x 1.5v-3v motors with 1:100 gear, loads of torque ! But they're heavy , and need shit loads of current (0.35A on 3V each !).
I need two massive h-bridges. But designing an h-bridge is subject for another thread :)


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