Wittmann Help with Schematic for reversing Herbie..

Hi Liam,
I thought that I would save you the trouble of starting a new thread about the acuracy of the schematic for a directional reversing Herbie.Thank you for the suggestion of buying a kit but since I am so new to 'Robotics', I am a bit reluctant to buy a kit from Solarbotics because it is quite alot of money ( especially in postage across the Atlantic ) when I can use a Schematic and parts to make my own for a fraction of the cost. I have a twin motored 5 Inch Dalek that used to be remote control and its just waiting to be 'Hacked' into a photovore, obstacle avoiding 'Herbie' !
Just in case people want to know I have a 'Hex Bug' that I have modified to carry 2 x AAA batteries on its back as they are cheaper and last longer than the button cells , a blue 'Stomper B.I.O. BUG' That I have drilled the edge of the ' Feet ' and have inserted the ends of cut down picture frame nails into with the pointy end facing out to give better grip off road on my grass and I have just built the ibotz ANTOID MR-1002 that I picked up off ebay for 99p......what a bargain !!!!! I realise that none of these needed any soldering but at least my Symet did and it worked first time so perhaps bread-boarding it first to check IS a good idea

[Liam_McQuellin]

Okay will i looked up the circuit you were talking about. I suggest going with the one that they describe to you in the tutorial, mainly because its a good way to learn to freeform off an IC (which is very handy as your circuits become more complex).

Im not sure what else i can tell you about Wilf Rigters mod apart from the fact that the light sensor circuit is relativly the same, just the turning curcuit is different.

If you really want to have a go at this one..

Breadboard it out, and see if that works.

Tommorow i will have a go myself and then ill take some pictures of the breadboarded circuit for you to copy if you like.

Good luck

Liam

Hi Liam,
Thank You very much for looking at the circuit for me, and it will be great if you could bread board it as my parts will not arrive for another week or so at the earliest.
The main part that I doubt as being accurate is the motors where they link to the LM386 chip on pegs 5 and 6 .The schematic on page 165 shows one terminal of the bottom motor connected directly to the -ve on the battery and the reverser circuit. One terminal of the top motor is connected to the +ve on the battery and to peg 6 and to the reverser circuit. THEN both the remaining terminals of the motors are connected to peg 5 !!! SO this means that the top motor has a +ve terminal and needs peg 5 to be a -ve to turn and the bottom motor has a -ve terminal and needs peg 5 to be a +ve to turn ........surely peg 5 can only be either +ve or -ve and NOT both. I cannot see that it could switch between both +ve and -ve because the robot would then move forward in a series of jumps as first one motor and then the other was powered up with its circuit being made. I hope that I have explained my concerns clearly enough to you. If not ask me and I will try again.
Using the tutorial is a good idea but the Herbie HAS to have a reverse function to get itself unstuck from obstacles in its path !!! The schematic on page 137 has each motor with the 2 terminals each connected to +ve and -ve, so they will work fine together. The only part that I don't like is the fact that it reverses BOTH of the motors so the Herbie moves forward until it hits an obstacle then reverses STRAIGHT back for a time and then drives forward again and it will hit the same obstacle in the same place. So I would rig it up so that only 1 motor reverses; this way the Herbie moves bacwards through 90 degrees and then moves forward and hopefully misses the obstacle or at least hits it in a different place !
Thanks again,
Wittmann

Many Thanks

[Liam_McQuellin]

Gday Mate,

So, i breadborded the circuit tonight. Works okay. Think i messed up something, or, thats just how the circuit works. It doesnt reverse. The motors just change direction.

Hang on. I just checked the direction of the motors in they do indeed go in different directions.

So, because ive never built this circuit before, i am not to sure of how it is to be set up. I will keep playing with it over the night and see what i come up with.

If you like, try this circuit. It is very simple to make and does work well. All the electronics are avaliable at an electronics parts store.

Hi Liam,
Thank You for the help. I am sorry to say that I have got the wrong kind of the 74AC240 processor I bought surface mount, so I am going to run with the LM386 as I have them ( and it has less pins to solder )
Hopefully I have just attached a diagram to show you the circuit that I intend to use . Although looking at it with my 'Non-Electronic-person' eyes I think that I see the SAME problem with tracing the +ve and -ve to the motors !!!!!! ..............PIn 4 , Bottom left, connects to -ve and to one half of the LOWER motor relay . The other power connection to the relay has to be +ve ( To operate the motor ) and connects to Pin 5 ,Bottom Right, and then carries on to one half of the UPPER motor relay. The other half of the top motor relay goes to Pin 6 >AND< to +ve !!!!!!......SO Pin 5 will have to alternate +ve and -ve to make each motor work in turn........is this how the circuit works and controls the phototrophic behaviour ????????????.........I may well have to bread board it and see if it works........this stuff seems confusing !!!

[Liam_McQuellin]

Did you have a go at assembling this circuit? What was the outcome?

Havnt had much time to build anything recently. I might give that circuit a go and see what happens.

Liam

hi is dat circuit above feasible???

[Liam_McQuellin]

I assume your talking about the circuit using the LM386 IC? Yea that one works well.

Hmm, I'm sure that I have seen an LM386 herbie that only uses a single relay for the turn and reverse behaviour.

[Liam_McQuellin]

You have,

Its featured in the JBB book. That diagram is one of the expansions to the original circuit to give more complex behavior, as in, just uses two feelers to determine the direction change.

Liam