Society of Robots - Robot Forum
General Misc => Misc => Topic started by: voyager2 on June 21, 2010, 09:20:49 PM
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Hi All,
Firstly this topic is for you to see my robot fish.
It has not been built yet but when I do I'll post pictures here for you. ;)
In the mean time I'll post the schematics, diagrams and development pictures.
This is my first pic ever uploaded to Photo-bucket. 8)
(http://i865.photobucket.com/albums/ab214/voyager64/RobotFish1.jpg)
I haven't drawn in wires or sensors, so the picture is not cluttered.
Its not quite scale for instance the battery is too small and the ATmega too big.
I've clearly labeled everything in block letters (including the volume of each segment!) so everyone understands it.
The servo controller is to power the electro-magnet.
Resistor R1 is for the LEDs while R2 fools the servo controller into thinking it's centered. ;D
EDIT:Does any one know of a good (free)3D CAD?
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EDIT:Does any one know of a good (free)3D CAD?
Google Sketch-up.
http://sketchup.google.com (http://sketchup.google.com)
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Have you tried eagle cad? I know if you are a student and you go onto the autodesk website you can get autocad for free but that may be just for highschool students....
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Thanks I'll try sketch-up.
I'm in year 6 so money, parts and money again come at a premium!
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I'm adding to the robot fish "data base" the inspirational YouTube video that started it all ;D
Small robot fish powered by solid polymer fuel cell : DigInfo (http://www.youtube.com/watch?v=bVTpINHJeaY#ws)
And here is another thead dedicated to the batery ::) (http://www.societyofrobots.com/robotforum/index.php?topic=11337.0)
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What is the bridge rectifier for ???
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What is the bridge rectifier for ???
The Bridge Rectifier is part of the Voltage Regulation circuit, and makes sure the voltage going into the Electro-Magnet is DC and the right polarity.
It's not really necessary but it's worth showing how to use them ;D
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Erm... Why wouldn't the voltage be dc in the first place?
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I understand what you mean SmAsH, in general it makes sure the voltage going to the IC and and coil controller is the correct polarity.
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Why not use a diode?
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A rectifier is a group of 4 diodes.
If I use a diode it won't work at all if the battery is in the wrong way, but with a rectifier the battery can be attached with any polarity.
Besides I have only 1 diode but I have plenty of rectifiers, and I get extra marks for "exotic" components ;D
EDIT: fixed typo
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Hi All,
Here is a list of the parts I'm going to use:
Battery http://www.sparkfun.com/commerce/product_info.php?products_id=8818 (http://www.sparkfun.com/commerce/product_info.php?products_id=8818)
Microcontroller http://www.sparkfun.com/commerce/product_info.php?products_id=7957 (http://www.sparkfun.com/commerce/product_info.php?products_id=7957)
"Signaling" LED's http://www.sparkfun.com/commerce/product_info.php?products_id=528 (http://www.sparkfun.com/commerce/product_info.php?products_id=528)
Magnets will be hand made.
Casing will be hand made.
Tail will be hand made.
Already have the rectifier.
Already have the regulator.
Oh and the coil controller is undecided as yet.
Next Post: Specs
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Rectifier = two diodes in circuit, which means a 1.2 volt volage drop! Lots of wasted power there.
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Besides I have only 1 diode but I have plenty of rectifiers, and I get extra marks for "exotic" components ;D
Only in a University do you get credit for a wasteful expenditure. In industry you would lose your job at worst, or be told to quit wasting money at best.
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Ok I'll take the rectifier out.
Next post I'll have an updated diagram and a diagram of the tail mechanism
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If there is a possibility of connecting power in reverse polarity then the bridge rectifier is not a bad idea. The Microchip PICDEM-2 board uses a bridge rectifier on the power input. This allows a wall wart PS with either + on the tip or the ring of the coax plug to be used.
In my designs for commercial products (research lab instruments) we try to design so that a user does damage the equipment if connect wrong. We always protect the power input from reverse polarity with either a series diode, if the circuit can accept the voltage drop, or a fuze and shunt diode. We consider this cheap protection.
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If there is a possibility of connecting power in reverse polarity then the bridge rectifier is not a bad idea. The Microchip PICDEM-2 board uses a bridge rectifier on the power input. This allows a wall wart PS with either + on the tip or the ring of the coax plug to be used.
In my designs for commercial products (research lab instruments) we try to design so that a user does damage the equipment if connect wrong. We always protect the power input from reverse polarity with either a series diode, if the circuit can accept the voltage drop, or a fuze and shunt diode. We consider this cheap protection.
That's what I thought too Waltr, until Razor Concepts reminded me of voltage drop.
Rectifier = two diodes in circuit, which means a 1.2 volt volage drop! Lots of wasted power there.
A rectifier has four diodes in a circuit.
...Only in a University do you get credit for a wasteful expenditure. In industry you would lose your job at worst, or be told to quit wasting money at best.
GearMotion, my teacher is obsessed with us using silicon chips in our projects so weget extra marks ::)
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Rectifier = two diodes in circuit, which means a 1.2 volt volage drop! Lots of wasted power there.
A rectifier has four diodes in a circuit.
Yes but only two are a the voltage path, one in the negative lead the other in the positive lead. The other two are reversed so do not conduct. Sounds like you don't truly understand the full-bridge rectifier so draw it out and trace the voltage paths.
For battery power curcuits a series diode isn't the best choice because of the voltage drop and waste power. That is where a series fuze and a shunt diode gives protection without power loss.
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"GearMotion, my teacher is obsessed with us using silicon chips in our projects so we get extra marks"
I'm not stopping you from doing what you need to do to get extra marks. I just wanted to point out that teacher's are very often far removed from industry. Just wanted you to pause for a moment and learn that complexity for the sake of complexity only looks good in an academic setting.
If you can justify the bridge, great. It has the benefit that you mentioned. It also has the negatives that have been mentioned. You need to weigh them against each other.
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I'm sure getting a diode will be fine, theirs still some silicone in them (i think)
Low voltage loss (at least less than the rectifier), serves it's purpose well too.
If sparkfun comes out with 6 v button cells @ 400mAh I'll use a rectifier...
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Hi,
If sparkfun comes out with 6 v button cells @ 400mAh I'll use a rectifier...
Two lithium cells stacked should do.
The consideration as to either make it "lots of silicon" or efficient in an academic setting doesn't matter much.
If you go for the inefficient, you just go critical about it in your written report.
Apart from that, if you want efficiency, either use a MOSFET or better yet, a fuse and a diode to do the protection without any loss.
After all, you have to be seriously dumb to swap polarity when you install it, with the focus you've had on it, so you'll probably never have to replace the fuse.
If you wanna go fancy with silicon, a better way would be to make it actually serve some purpose - even a teacher should be able to see through silicon added just for the teachers sake and purposefull silicon - they're not stupid, just out of synch. with the real (electronics) world.
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Hi,
If sparkfun comes out with 6 v button cells @ 400mAh I'll use a rectifier...
Two lithium cells stacked should do.
Thats what I'm going to do, 6v @ 200mAh is going to be fine for me.
...Apart from that, if you want efficiency, either use a MOSFET or better yet, a fuse and a diode to do the protection without any loss.
After all, you have to be seriously dumb to swap polarity when you install it...
I see what you mean, but if your in a rush polarity is the least of you worry's.
I'll just use the diode method, I'm sure I can find one, somewhere.
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This is the sketch-up file!
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What material should I make the case out of?
I thought of milk carton plastic and Silicone-Rubber.
I don't have a Laser Cutter or Vacume Forming machine so my options are limited.
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I found this elrctro-magnetic actuator
Electro-Magnetic Actuator (http://www.microflight.com/Online-Catalog/Actuators-and-Servos/MiniAct-Magnetic-Actuator-1-1g)
Perfect!
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That will not be strong enough to work underwater. Even in open air, that actuator cannot move unless it is moving forwards.
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Thanks for pointing that out Razor Concepts.
I never really know "g-cm" means
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Here's a few more pictures...
(http://i865.photobucket.com/albums/ab214/voyager64/RobotFish3.jpg)
Demonstrating turning.
(http://i865.photobucket.com/albums/ab214/voyager64/RobotFish4.jpg)
And the updated internals.
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Still waiting for the milk to run out...
I hope the pictures are clear.
I'm doing the paper template today, so I should have a fish-like case within a few days.
Just found out that the last tube of silicone-rubber was used for something else :-\ >:(
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This is a really ambitious and cool project!
Was looking at your original design and have been wondering what materials your use to make it sufficiently water proof and how the tail will move. Are you going to use micro controllers for that? I think the tail part is such a simple and efficient design, just points out further that nature has the best designs that can be transfered to robotics (insect design of 6 legs being more stable then 2). Really looking forward to seeing this project progress, best of luck!
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frostyg02uk the tail is driven by two round Electro-Magnets.
In the middle is a little metal "hammer" that is attracted by the magnet.
A pivot allows the "hammer handle" to swing back and forth, in turn driving the tail.
I'll use a plastic milk carton(cut up)to form the body with silicone-rubber to join it all up.
Yeah it is a bit ambitious for my second project...
Suppose its better then that 18dof humanoid...
Voyager2
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I see wow. Well I guess why do something easy that everyone has done and not be challenged. Ambitious is the way to go! Im certainly rooting for your success
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OK to clear it up for everyone else I've attached a Google-Sketchup file (zipped) that shows the tail mechanism.
Red shows the pivot, dark grey shows the electro-magnets, white shows the metal "hammer", and light grey shows the tail.
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Hi,
If you move a (2 part?) coil with fixed magnet(s), you'll have less mass to move.
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Hi All,
Hi,
If you move a (2 part?) coil with fixed magnet(s), you'll have less mass to move.
Do you mean have the electro-magnet in the middle on the boom/arm/thing and have permanent-magnets on either side?
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most likely, yeah
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That sounds pretty smart... If you put on on each side with attracting ends going towards each other. This not only increases the secure-ness of the attachement, but it also makes your hammer idea much more powerful.
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Hey, I had an idea...
If you were to find a non-flammable epoxy resin coating, you could use it to waterproof all of your electronics... Provided they are already in circuit.
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So heres the new tail mechanism.
http://www.filesend.net/download.php?f=5e320258bc5d6b750e958e7c7c57fd30 (http://www.filesend.net/download.php?f=5e320258bc5d6b750e958e7c7c57fd30)
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Hi All,
I'm thinking of powering the electronics with a 10F super cap like the ones from SparkFun.
The coils can be powered with the two batterys 3v @ 400mAh.
Does anyone know of a place I can get 2 MOSFETS that can handle 800mAh(I want some overkill ones)
Voyager2
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fishy fishy
Voyager2 asked me to post something here so I did lol
btw on a serious note, how do you mean you'll just use a capacitor to power the MCU?
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Super caps have very very high capacity that can basically be used as a battery. I would not reccomend it as it can easily fail, which is bad in a fish.
I like fairchilds logic level mosfets, they work at 4.5 volts which is excellent. Something like a FDS6680 would work nice
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Super caps have very very high capacity that can basically be used as a battery. I would not reccomend it as it can easily fail, which is bad in a fish.
I like fairchilds logic level mosfets, they work at 4.5 volts which is excellent. Something like a FDS6680 would work nice
Do they work at 5v too, and can they be switched directly from the MCU?
I had a wacky idea, can i split the battery so it provides 3 @ 400mAh, from one set of conections, but can supply 6v @ 200mAh from another set?
I'm going to have two batterys at 3v @ 200mAh each...
Voyager2
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umm... not entirely sure what you mean, but the mAh rating is just the capacity, so the components will only use as much as they want depending on their current draw. but you can have a 6V battery go to a regulator to 3V to power some comonents and also have the same battery power a motor for example at the 6V, or use a 5V regulator so its a little more stable.
[6V Battery] -> [3V regulator] -> [all 3V components]
|-> [5V regulator] -> [all 5V components]
for this to work you'll just need to have a common ground.
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No I mean have the battery I parallel to provide 400mAh @ 3v + have them in series to provide 200mAh @ 6v, both at once.
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Seems like a bad idea...
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if 2 batteries are parallel their voltages don't add up, 2 3V batteries running parallel will just be 3V,
if you want 6V you'll need to run them in series.
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You can become a Robot Fish volunteer!
Send me free stuff and you get your name in extra-large on my site (its under construction)
To volunteer send me a PM.
Note, as a volunteer you will not ask for payment, you will have to pay for stamps, etc.
Not bad if you live in Oz, stamps are only 60c(they went up in price >:()
The following items will be accepted as "donations"
- New micro-controller(I only have ATmega 168's :()
- One set of electo-magnets
- Battery's(not leaked)
- Appropriate sensors(photo-resistors,bump-switches, etc.)
- Appropriate high current transistors/MOSFETs
- Assorted robot "stuff" that can fit in an envelope
Want to donate?
Send me a PM or e-mail me([email protected] with your name(full), e-mail and the type of part you want to send.
I will e-mail or PM you with my address.
I am not responsible for lost, damaged or misdirected mail
Voyager2
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Oz? With wicked witches and yellow roads ???
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Oz? With wicked witches and yellow roads ???
Australia you Yank ;D ;D ;D ;)
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i think that it will be more effective for you if you just make an order from a site for components like MOSFETs, photo resistors and bump switches. most people chose to keep these as they are always handy as you never know when they may come in handy.
don't deem what is and isn't acceptable, be great full for anything that comes your way considering what your asking.
if you offer to pay shipping you might get a couple of things that people don't need any more etc. asking people to pay shipping is a big ask as shipping for some items cost quite a bit.
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Ok i can pay for shipping, anything less than five dollars(AU$) though.
But I cant pay the donator, I will allow "Replied Payed".
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I've removed the attached item from my previous post, and added a link to download it from FileSend.
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Hi,
Does anyone know of a place I can get 2 MOSFETS that can handle 800mAh(I want some overkill ones)
None that can be run off 3V!
Why do you want MOSFETs?
BjTs like BC327 and/or BC337 (depending on what polarity you need) will do fine for you - or get their equivalents from Zetex to get the lowest V_ce_sat (the voltage drop) possible.
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They have to switch at 3.3volts, not 3 volts.
They need to switch the tail electro-magnets.
3.7v will be the maximum they switch
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Just for anyone interested, i'm going to call my fish:
FRANK STALLONE : the robot fish ;)
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My first fish body was rather horrible, believe me, it was horrible!
But lucky you, I made a second one which i call, V2
Here are some pictures, not quiet complete though:
(http://i865.photobucket.com/albums/ab214/voyager64/Robot%20Fish/Fishfront.jpg)
(http://i865.photobucket.com/albums/ab214/voyager64/Robot%20Fish/FishSide2.jpg)
(http://i865.photobucket.com/albums/ab214/voyager64/Robot%20Fish/FishSide.jpg)
Note the hole in the side, that's where wires, waterproof connectors and other interesting stuff will come out.
The hole in the back is where the EMs, AVR, etc. will be slotted in.
Current Progress:
Body 50% (Body V2 is under construction, V1 was embarissing)
Electronics 10% (Got almost all componets)
Mecanics 25% (Electromagnets in mail, tail is made)
Software 5% (Know how it is going to work, but need electronics)
Please excuse the fact that much of this is copied from:
http://letsmakerobots.com/node/21982 (http://letsmakerobots.com/node/21982)
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Haven't fully understood how it's going to work, but good luck!
No point in using MOSFETS, just use transistors, 800mA is NOT high current, and that sparkfun 10F capacitor can only handle about 2v.
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Thanks for pointing that out Razor Concepts.
I never really know "g-cm" means
The g-cm is a measure of torque just like lb-ft. In your case the actuator has a torque of 2.61g-cm. This will be easier to think of with a left-right actuator than with a standard rotational dc motor. From the actuator, if you go a centimeter out from the actuator's head, then it can move 2.61 grams back and forth. But I highly recommend you do some tests before you get that actuator(Even if you use two or three at a time). As the resistance of the water will increase the force necessary to move the fin back and forth.
Also try to make the fin as hydrodynamic as possible, to reduce "blocky" surface area which would slow down the movement of water going around the fin.
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Good to see that you've started the actual build. I find that if I leave it to long I lose interest
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Hi All,
I've been researching different ways of propelling my fish, all 4 of my electromagnet attempts have failed, and instead I'm going to use a servo.
I have therefore emptied my money box to buy this little guy from a local hobby shop:
(http://i865.photobucket.com/albums/ab214/voyager64/IMG_6745.jpg)
HS-65HB Mighty Feather servo.
Came with 2 extra horns and 4 screws for mounting, a good $28 spent!
Haven't powered it up yet but apparently it can supply 2.2kg-cm @ 6v
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That servo when used properly is great quality. it is popular at the model aeroclub i am a member of. it is commonly used in small nitro planes with great results.
What are your plans for this drive systems?
looking forward to seeing the design!
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I'll upload a CAD later but the general idea is that a little piece of solid core wire is threaded through a hold in the horn, that bit of wire is attached to a lever that drives the tail.
Since its so small I'd love to see a continuous rotation mod for it...
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I have heard that they can be a bit temperamental. the most important thing to take into consideration the structure of the gear. just because of the size they become a lot harder to work with. but if you do it bit by bit with a file or something similar and put little stress on the servo then you shouldnt have a problem.
have a look in the memebrs tutorials section as i think there is a tutorial on how to mod a micro servo like yours.
Good luck
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I'd never really need to mod it, just thought it would be cool to see one modded
Here's the CAD I through together:
http://www.filesend.net/download.php?f=fc8a0ad02db64c03bb20be6f2bd983c5 (http://www.filesend.net/download.php?f=fc8a0ad02db64c03bb20be6f2bd983c5)
The servo is over-sized, and the little wires coming out of the horn are not quite right.
The little "plate" on the end of those wires is hinged (that wire/rod thing is the pivot) and the tail is attached directly to it.
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it all looks good, looking forward to seeing the build.