Another Animatronic Cannon!
- Thread starter Honus1
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This thing is amazing! Those Iron Man props you've made are excellent too.
I was hoping to do something like this myself eventually; I spent the last year designing an Arduino-based microcontroller specifically for this sort of animatronic prop... but I wasn't planning to sell the things fully assembled with machined parts and all the gearing!
(Btw, that RFID tag idea is genius.)
I was hoping to do something like this myself eventually; I spent the last year designing an Arduino-based microcontroller specifically for this sort of animatronic prop... but I wasn't planning to sell the things fully assembled with machined parts and all the gearing!
(Btw, that RFID tag idea is genius.)
Thanks! A while back I made a multi purpose servo driver board based on the 3.3V Arduino Pro Mini- http://www.instructables.com/id/Arduino-animatronics-make-your-awesome-costumes-m/sswift said:
Sort of. I do it because servos should always have their own isolated power supply as micros are pretty sensitive to noise generated by the servo motor which can result in glitches and erratic dervo movement. You can power everything from a single battery but the micro must be run from it's own regulator. Probably as a result of following this practice I've never had audio issues.sswift said:
I haven't noticed any issues with glitching due to the servos being powered by the same battery, but I did find that I couldn't run more than eight or so if I was running off some AA batteries. That issue however I'm pretty sure is due to a voltage drop caused by the batteries being unable to provide the short burst of power needed when the servos start up or change direction, and I expect that if I had some LiPos instead it would go away.
The noise issue however was severe. I really want to be able to run the microcontroller and servos off the same power source because it's more convenient for the end user, and my board is designed to fit in small handheld props where there's no room for two sets of batteries and I'd like to be able to put servos in those as well. I was thinking about creating a board with some bulk capacitance to go between the microcontroller and battery. That might be enough to prevent the noise from getting into the audio circuit. I haven't had a chance to test it though.
The noise issue however was severe. I really want to be able to run the microcontroller and servos off the same power source because it's more convenient for the end user, and my board is designed to fit in small handheld props where there's no room for two sets of batteries and I'd like to be able to put servos in those as well. I was thinking about creating a board with some bulk capacitance to go between the microcontroller and battery. That might be enough to prevent the noise from getting into the audio circuit. I haven't had a chance to test it though.
What I usually do is run the servos from the battery and then run everything else from a drop down DC/DC converter to isolate it. Works perfect when you want to use a single battery pack power supply and all you need to worry about is making sure your battery pack can support a high enough discharge rate to power all the servos- sometimes this can be an issue if you're using a lot of digital servos as some of theose servos can pull some serious current. The reason I run everything but the servos from a drop down converter is you get a stable 5V and you usually don't need high current capacity so heat sinking isn't a problem. You can do it using a 7805 5V regulator too or you can use 6V battery pack with a 3.3V regulator if your micro runs on 3.3V. DC/DC converters are just a lot more efficient. A lot of how I do it depends on the type of servos I'm using and what the current/voltage requirements are. I usually prefer using LiPo packs so if I have high voltage servos then I power the servos from the battery and if I'm using lower power analog servos I'll power the servos from a high current DC/DC converter. I have to say I really like the newest digital servos for their versatility and power.
I've got one pretty complex prop I'm working on right now that is powered by a single cell LiPo and I'm using 5V step up converters to power the servos. This way the micro is powered by the LiPo directly and I have built in charging over USB.
I've got one pretty complex prop I'm working on right now that is powered by a single cell LiPo and I'm using 5V step up converters to power the servos. This way the micro is powered by the LiPo directly and I have built in charging over USB.
I do use a switching buck regulator with my kit, but the issue with that is my microcontroller runs on 5V, and to supply 5V it needs a little over 6V, and a 7.4v LiPo would burn out your typical servo, so running the microcontroller from the regulator and the servos directly from the battery isn't possible, unless of course, you get high voltage servos. Those will run at 7.4v; but they're a bit more expensive.
Of course standard servos could run off a 4.8v battery, but then you'd have to run the microcontroller directly from the battery as well. With proper decoupling capacitors in place that might be okay, though I haven't tested it.
And running off 6V isn't an option because the switching regulator requires a little over 6V and besides, for these high current applications rechargables are the better way to go so you're not replacing batteries constantly.
Anyway the big disappointment for me is that I specifically designed my boards to have the same pinout as servo connectors use so the servos could just plug straight into the board. And that works just fine, so long as you don't have sound. It's nice that there's a workaround for the issue, but if I ever do a version 2.0 I'm gonna have to look at ways to better isolate the audio system. Or switch to 3.3v operation. But having 5V output on the ports is awfully convenient, and I'd still need 5V for the audio if I want to get 2W out of the amplifier.
Of course standard servos could run off a 4.8v battery, but then you'd have to run the microcontroller directly from the battery as well. With proper decoupling capacitors in place that might be okay, though I haven't tested it.
And running off 6V isn't an option because the switching regulator requires a little over 6V and besides, for these high current applications rechargables are the better way to go so you're not replacing batteries constantly.
Anyway the big disappointment for me is that I specifically designed my boards to have the same pinout as servo connectors use so the servos could just plug straight into the board. And that works just fine, so long as you don't have sound. It's nice that there's a workaround for the issue, but if I ever do a version 2.0 I'm gonna have to look at ways to better isolate the audio system. Or switch to 3.3v operation. But having 5V output on the ports is awfully convenient, and I'd still need 5V for the audio if I want to get 2W out of the amplifier.
I'm not sure what your setup is like, and I'm sure it works fine, but I looked at step-up converters when I was desgining my boards... and not just what is readily available from hobby stores... I used Texas Instrument's power design tools to search for regulator designs I could implement myself on my board... and what I found was that step-up regulators don't seem to be able to supply much power. If you're using one per servo then I could see you getting away with it, but I don't think I found one design that could supply more than 800mA or so, and one regulaor per servo is an expensive way of going about things.
Haha! Welcome to my world! Accounting for the voltage headroom for regulators is always a PITA. Now you know why I like high voltage digital servos- LOL! Of course there are very few micro servos that are 2S compatible...
I use both 3.3V and 5V boards and have just learned that I have to make a choice depending on the given application and types of sensors and servos I'll be using. There just isn't any one best answer. Generally speaking, using the 3.3V boards tends to give you more options for battery power- you can power most all servos from 6V packs and then drop down the voltage to 3.3V for your micro and then use a 5V boost converter from that to power your sound board since most sound boards to require too much power from the boost converter. It's not necessarily the absolute cleanest way to do it in terms of design but everything will get good clean regulated power and you don't have to dissipate a lot of heat.
The project I'm working on now will have a boost converter for each servo- it's really the best way to do it for this particular project given all the design requirements. I did find one converter that went up to 1A- I'll have to see if I can find the datasheet for it.
I use both 3.3V and 5V boards and have just learned that I have to make a choice depending on the given application and types of sensors and servos I'll be using. There just isn't any one best answer. Generally speaking, using the 3.3V boards tends to give you more options for battery power- you can power most all servos from 6V packs and then drop down the voltage to 3.3V for your micro and then use a 5V boost converter from that to power your sound board since most sound boards to require too much power from the boost converter. It's not necessarily the absolute cleanest way to do it in terms of design but everything will get good clean regulated power and you don't have to dissipate a lot of heat.
The project I'm working on now will have a boost converter for each servo- it's really the best way to do it for this particular project given all the design requirements. I did find one converter that went up to 1A- I'll have to see if I can find the datasheet for it.
Cool, I'd like to take a look at that datasheet if you can find it. I do use a boost converter with my kits for one thing... 12V LED bulbs designed for cars. I can get these tiny 1W-3W bulbs with like 17 high powered LEDs on them in an extremely compact form factor with a couple pins that I can plug standard pin header connectors into, and they're cheap to boot.
Here's a 1.5W bulb I used in a crappy arc reactor I threw together in a half hour for fun:
The photo doesn't really do it justice, it's bright enough to be hard to look at, and I use ones twice as bright as strobes with a kit I sell for a different prop.
The thing wrapped in blue tape is the 12V module of my own design, it takes 5V+ in and steps it up to 12V, and there's a signal pin on it so the microcontroller can switch it on and off. It's on by default, so I only needed to plug in a battery here to get 12V out.
Here's a 1.5W bulb I used in a crappy arc reactor I threw together in a half hour for fun:
The photo doesn't really do it justice, it's bright enough to be hard to look at, and I use ones twice as bright as strobes with a kit I sell for a different prop.
The thing wrapped in blue tape is the 12V module of my own design, it takes 5V+ in and steps it up to 12V, and there's a signal pin on it so the microcontroller can switch it on and off. It's on by default, so I only needed to plug in a battery here to get 12V out.
Here's the info for that boost converter.- it's a Linear LT1308. It'll provide 5V @ 1A. http://www.linear.com/product/LT1308#overview
That's a pretty slick lamp setup. For high power stuff I've only used Luxeon high power LEDs with a contant current buck driver.
That's a pretty slick lamp setup. For high power stuff I've only used Luxeon high power LEDs with a contant current buck driver.
You should also check out this litte gem- it's a step down switching regulator that will supply 5V @ 1A with an input voltage range from 6.5V to 32V. It also comes in a 3.3V version.
http://www.adafruit.com/products/1065
http://www.adafruit.com/products/1065
That's a neat little package, but awfully expensive. I'm sure a similar spec regulator of the same size could be found or less than half that.
Here's one for example which outputs 600mA and is less than $6:
http://www.pololu.com/catalog/product/2107
But here's something even better... a regulator which can take an input between 2.7v and 11.8V and output 5V:
http://www.pololu.com/catalog/product/2123
Typical output ranges from 500mA to 1A depending on input voltage. Also available in 3.3V version. And it's also less than $6.
Here's one for example which outputs 600mA and is less than $6:
http://www.pololu.com/catalog/product/2107
But here's something even better... a regulator which can take an input between 2.7v and 11.8V and output 5V:
http://www.pololu.com/catalog/product/2123
Typical output ranges from 500mA to 1A depending on input voltage. Also available in 3.3V version. And it's also less than $6.
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