Hi All

Does anyone know what circuit i can use to make a dc motor randomly move backward and forward, stop for a period of time and then start again? Any help and ideas will be much apreciated.

Thanks Edward

 

Connect an H-bridge to a microcontroller and have the microcontroller randomly drive it.

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I don't know much about Microprocessors? So could you possably give me a circuit diagram and maybe explain it.
Thanks

 

Here's the Mongoose schematic (a robot kit) with a Microcontroller and H-Bridge

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Is this the easiest option their is?

 

Yes, it is.

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could anyone possably explain the circuit to me and also show me exactly where and how everything goes

 

Step 1:
Google "H-bridge" and learn how they work and let you drive a brushed DC motor in both forward and reverse.

Step 2:
Google and read about how to wire up PICs. In the simplest sense, it involves wiring up power through a simple voltage regulator IC, some bypass capacitors between V+ and ground to stabilize the voltage, and wiring up the oscillator. A lot of microcontrollers now also have an internal oscillator so if that is good enough you don't even need to wire it up an oscillator (just power). How much easier can it get?

Example from some random website:
http://www.andrewkilpatrick.org/mind...ic_circuit.png

Google around for SIMPLE PIC circuits that do different things and compare the similarities between them. THat's what is needed to wire up in the most basic form.

A good start for H-bridges:
http://www.modularcircuits.com/h-bridge_secrets1.htm

THere are some things that are too vast, take too many words and unwarranted to take you step-by-step through them on a forum. Come back after you've done some of the reading and ask specific questions that will be easier for us to answer, and for you to understand the answers to. If I waste my time spitting out a huge chunk of text, you still probably wouldn't understand it because that's just the way it is. We aren't exactly here to hold your hand (and your last post irked me quite a bit in the "exact" nature of the request and wording because it seems to indicate a complete lack of effort on your part).

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blueroom, I think it's just funny the way your little avatar seems to look at the schematic for the mongoose. (Like are you sure you want to do this ? Or I really don't think he knows what he's getting himself into.)

............ lol

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TO simplify BLueroom's schematic, you can probably chop off everything to the left and top of the PIC in the middle, leaving only the stuff to it's right, and the motor part to the bottom. In his schematic, he used an H-bridge IC rather than one of discrete components (The SN75410).

No regulator is in the circuit for the PIC so one should be added. A starting place to look at is how to use the LM7805. It's very simple, you should have no problem understanding how it's used if you take a glance at the datasheet (or the datasheet of any other linear regulator). I have no idea what those optocouplers are for on the top-right of the schematic so you can ignore those too.

Notice the H-bridge has uses the "raw" voltage (or a different voltage supply) from the PIC. The PIC uses a voltage that has been cleaned up by a regulator (not shown)

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Anyone ever made something like this as a toy for the cat? Could be very entertaining!

 

dknguyen, I am not following you logic regarding the need for a regulator in the previous post. I use the TO92 sized 100mA LDO regulators to supply my robot uC's.

Why does the uC require a regulator? Isolation? Without regulation you will be able get more time out of the battery.

To use a 5V regulator you need more then 4 cells to get enough headroom for a regular regulator to function.

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The PIC is not regulated and is quite happy with a 4xAA NiMH power source (about 5V, originally PICs were designed to handle 7VDC). Even better the 18F2525 (and many other 18F series PICs) have a built in low voltage detector and can set an interrupt when VDD drops below a setpoint.
A linear regulator is just going to sap precious power from your batteries, and require a higher power source to boot.

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I would be more worried about the requirements for V(logic) for the SN75410. Maybe the 4.5V min in the datasheet has some flexability? Doesn't seem like a lot of headroom there.