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Any advise for this robot schematic?

kcoer

Dec 20, 2013
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http://imagizer.imageshack.us/v2/1600x1200q90/850/xf2g.png


NEW http://imageshack.com/a/img853/9579/ygtv.png


The device will switch polarity for 2.5 seconds when the momentary switch in the top left corner is hit. Motor 1( which is not in the schematic but you can tell where you would put it )will shut off for 2 seconds every 10 seconds. The 555 in the top left may not be configured correctly. Any advice i could get would be great. Does anyone know if I am using the inverter and transistors correctly. I made it myself(as you can probably tell). THANKS
'
 
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davenn

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hi kcoer
welcome to the forums :)

you have given us far too little information for anyone
to respond with any worthwhile input

specifically what sort of advice were you after ?
what's it supposed to do ?
is it your own cct or one you found somewhere?
is there any operation description you can link to ?

Dave
 

(*steve*)

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kcoer, let me give you my analysis...

When I first looked at this I saw that the output of U2 controlled the transistors Qll and Q12, Q12 being driven by an inverter. This looked to me like it might be intended as the beginning H Bridge, and the fact that the bases of Q13 and Q14 are likewise controlled made that seem like a starting point. It seemed that U2 controls direction, and U3 (vua Q16 turns the motor on and off (perhaps to control speed via PWM?)

OK, that's the working hypothesis.

However I discarded it almost immediatly because whilst the outputs labelled + are not unreasonable, the outputs labelled - are not.

Looking further, the load being in the emitter of Q13 is problematic, but the wiring of Q14 is simply diabolical. It will potentially short the output of U2 for not reason I can comprehend.

In addition to this, the power supply to U2 is switched by U3, and that seems odd.

Finally, the lack of base resistors will lead to another set of problems (including the possibility of frying components).

On the basis if this analysis, whilst I can't tell what you're doing, I can tell you that:

1) it's not an H bridge
2) it's not going to work
3) You're not using the components correctly.
 

kcoer

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http://imageshack.com/a/img853/9579/ygtv.png


(*steve*) I should have explained everything before asking for advice( like davenn said ) this would help everyone with giving advice.

In the updated circuit I used a DPDT relay instead of a H bridge. Base resistors have been added. U3 will cut off the power supply for two seconds every 10 seconds. This will create a random turn to prevent the robot from going in the same direction for too long. U2 will power the DPDT relay when the switch in the top left is hit. U2 will reverse polarity for three seconds. That explains why U2 is switched by U3.

Also could you explain
the outputs labelled + are not unreasonable, the outputs labelled - are not
or have I already fixed this in the updated picture

This still leaves one problem. The voltage at the positive lead is 1.4 volts. Does anyone know how I could get the original 6 volts at the positive lead?
 
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kcoer

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BTW how do i delete a post?
 
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Arouse1973

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Kcoer
It looks like you are powering a timer from a 10k resistor through the npn. We would usually use a pnp as a power switch because of the lower voltage drop.
Thanks Adam
 

kcoer

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Thanks, but do you happen to know how to wire a h bridge or will a relay work better for this instance?
 

Arouse1973

Adam
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Is this just a motor or a servo? They are different beasts.
Thanks Adam
 

kcoer

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Do you happen to know why when I set this circuit up I get a reading of 1.5 volts at positive lead?
 

(*steve*)

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(*steve*) I should have explained everything before asking for advice( like davenn said ) this would help everyone with giving advice.

Yeah, and the other issue is that standard circuits are normally drawn in a standard way. This not only helps people identify them, but it allows you to see if you've drawn them correctly.

In the updated circuit I used a DPDT relay instead of a H bridge.

This will work, but typically the NO and NC connections are wires to the power and the common connections go to the motor. The advantage is that a stuck contact etc. on the relay will not risk shorting your power supply.

Base resistors have been added.

Umm, no. There is no resistor between pin 3 of U3 and Q1.

Also, what current is required by the motor? The transistor you have chosen may not be able to supply it. *and* the load is in the emitter, not the collector. Yo would be better off with a PNP transistor or a P channel mosfet (or switch the ground connection rather than the positive connection. In orfer not to change the way the circuit works, the latter suggestion of an NPN transistor or N channel mosfet switching ground would be better.

U3 will cut off the power supply for two seconds every 10 seconds. This will create a random turn to prevent the robot from going in the same direction for too long.

OK, not sure about random, but I get what you're doing.

U2 will power the DPDT relay when the switch in the top left is hit. U2 will reverse polarity for three seconds. That explains why U2 is switched by U3.

OK, but perhaps it is better if instead of switching power to U2 (and the 10K resistor isn't going to let it wok by the way) that you hold the 555 in a reset state for that 2 seconds? (See that reset pin?)

Also could you explain
the outputs labelled + are not unreasonable, the outputs labelled - are not
or have I already fixed this in the updated picture

You've fixed it. But if you're interested, google H-Bridge. Find one using bipolar transistors and compare what you had with it. Also not me very first comment in this reply.

This still leaves one problem. The voltage at the positive lead is 1.4 volts. Does anyone know how I could get the original 6 volts at the positive lead?

This is due to the way you have wired up Q1 and I have dealt with this above. In order to get anything like the full 6V, you will need to use a logic level N channel mosfet.

BTW how do i delete a post

What post do you want to delete?

We restrict deletes because they can make threads no longer understandable if you remove things people have replied to. The same goes with edits. If you change your question after people have answered it doesn't make sense any more (also people subscribed to the thread don't get notified so nobody answers your new question.
 

kcoer

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Updated even further http://imageshack.com/a/img196/6185/tael.png

Heres what I tried to do...

give U2 4 volts through a voltage divider.
Use a H bridge rather than a DPDT relay.

This might be off topic but the whole concept of ground confuses me. In a real life DC
circuit what is ground. Does this device even need ground?

Say I wanted to add some more features, I could add more 555 timers but using a micro controller sounds easier to use. One problem, I have no clue how to program. Is this a hard skill to develop or is it the way to go? I am willing to learn though;)

I agree, a n channel mosfet is the way to go.

In my H bridge do I need to use MOSFET's? OR PNP?
How should i have wired Q1?

My motor draws about 60 ma plus or minus 3.

If you havent already noticed I'm new to this stuff. Thanks for everyones time and MERRY CHRISTMAS
 

(*steve*)

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OK, you still have no base resistors for any of your bipolar transistors.
Place a 560 ohm resistor in series with each base connection.

The 1 ohm and 560 ohm resistors in parallel do nothing useful. Remove them.

Still not happy with the way to switch power to one of the 555's but if you really want to...
 

(*steve*)

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OK, here's the direct answers to your questions

Ugive U2 4 volts through a voltage divider.

No, you're not doing that, and in any case the 555 requires a minimum of 4.5V. As mentioned above, remove the 1 ohm and 560 ohm resistor in parallel.

Use a H bridge rather than a DPDT relay.

You've done that, but you've not placed any base resistors in the circuit.

A problem with driving this is that the 555 can't pull the output high enough to turn the top transistors properly. You could consider replacing them with PNP transistors, but then you may have problems turning them off!

The relay may be your best solution here.

This might be off topic but the whole concept of ground confuses me. In a real life DC
circuit what is ground. Does this device even need ground?

Sorry, I don't understand what you're saying.

The negative rail is usually labelled ground, but that is because it is a reference point for voltage measurements, you don't earth it or anything like that in most cases.

Say I wanted to add some more features, I could add more 555 timers but using a micro controller sounds easier to use. One problem, I have no clue how to program. Is this a hard skill to develop or is it the way to go? I am willing to learn though;)

A microcontroller is definitely more flexible, and as you correctly deduce, more complex as well.

There are several microcontrollers which are good for beginners. In all cases you'd probably want to get to know the microcontroller before you start a project for real. Look at PicAxe and Arduino, although there are many other options.

I agree, a n channel mosfet is the way to go.

How should i have wired Q1?

Q1, do you mean M1?

That's OK, except that you need a P channel mosfet. However you have the source, drain, and gate in the correct places. A gate resistor (of about 100 ohms) would be nice to have.

In my H bridge do I need to use MOSFET's? OR PNP?

I'd probably use logic level mosfets because you're operating from a low voltage and bipolar transistors may drop more voltage (that your motor may need)

My motor draws about 60 ma plus or minus 3.

Good, that's not too much.

However you will require diodes to protect the H bridge from transients. This is another reason why a relay may be easier for you.

If you havent already noticed I'm new to this stuff. Thanks for everyones time and MERRY CHRISTMAS

No problems. Merry Christmas!
 

kcoer

Dec 20, 2013
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Okay steve, I think I'm ready to build my bot!
But some LED's and a camera attracted to noise and motion would be nice.
To save power, a phototransistor would have the LEDs on only at night.
A buzzer/speaker to play music would add to the bot.
A paintball gun on top would be pretty cool.
I could probably add a laser diode sight to the pb gun.
I could add a receiver so i could Control the bot. Put three different modes in so if i wanted it to explore it could, if I wanted to control it I could push a switch, maybe put some boundaries on where it could go or no boundaries depending on the mode

Yeah you can buy this somewhere for 300$ but making it yourself would be cheaper and fun.

What kind of micro-controller do I need?
How do I need to arrange the motion and sound detectors?
I figured a 7 channel transceiver would work for this, 1 channel for camera servos, 1ch forward backward, 1 channel forward backward other motor, 1 channel for speaker, 1 channel for firing the pb gun, 1 channel for changing position of the pb gun, and 1 channel for raising pb gun up and down. The camera motion/sound detectors will be off in controlled mode.

How much money would a bot like this cost me????
 

kcoer

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I swear, I will 'DEBUG' the circuit before I ask for advice. 10 times better then the original circuit. I will learn how to program micro controllers and better circuitry practice. Is it best I post a new thread for this machine?
 

(*steve*)

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Okay steve, I think I'm ready to build my bot!
[...]
How much money would a bot like this cost me????

Perhaps you could stat by explaining what you want it to do. Your description misses most of it.

By the way, if you're planning on mounting any sort of gun on it, I won't be helping you.
 

kcoer

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Okay, I'll leave out the gun. Let me describe it further.

The new bot needs to be able to explore new places and return to some place after exploration. It needs to cross roads but look both ways before crossing. It needs a live camera. It needs LEDs that turn off and on. It needs to communicate with me. It needs to be a meter long, and 30cm wide. It needs a speed controller. It needs a speaker and many sensors. It needs a deployable boat.

In communication, I need it to send battery level, its geographic location, live dual cameras and speakers, a microphone, a speaker to send voice automated messages, and any other status of the bot needs to be reported. The speaker needs to be loud.

The boat needs a live cam and needs to be a quarter meter long and a 1/16 meter wide.
no speakers or mic on boat. The boat can only be deployed by the controller. the boat needs a separate battery that can monitored by the user.

Solar panels to fuel LEDs that come on at night.

Two electric motors should be good. Should I use a transmission?

I said sensors right? probably 3-5 motion and 3-5 that detect anything(and its position) within 5 foot. The bot will be programed to react to the switches that are triggered by rotating the camera the direction of the sensor.

The bot itself needs different controllable modes say 3 or 4.

Im in a time frame of 2 years and a budget of 500$.

If you cant help me, can you tell me what parts I need to get for any project like this?

How would I get into programming? What language should I learn?
 

(*steve*)

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Does this "bot" need to do all of these things autonomously? Or will it be remote controlled?

It sounds like a really ambitious project.

Have you ever built something simpler? Perhaps a white line follower?

Water and electronics really don't like each other. If you're talking amphibious vehicle, you need to seriously consider how you're going to seal everything up.

You get into programming by starting with simple projects and doing more and more complex things as you learn to master the craft.

The language isn't really important. Let's say you need to learn C.
 

kcoer

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Object C sounds good to me, I have a mac so i guess I could program apps after I learn, not really.

How would I go about learning object C? Any books you recommend? Any online programs?

How about the Arduino UNO for my first controller?

The "ambitiabot" is miles ahead. But its a goal. I haven't tried anything simpler yet except I recently built the 555 bot.

Before I go any deeper into electronics, I need to build my workplace past a tackle box with resistors and a breadboard. What do you recomend?
 
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