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Possible Shield Requirements Analysis
05-13-2014, 11:36 PM (This post was last modified: 05-13-2014 11:37 PM by jmccartney.)
Post: #11
RE: Possible Shield Requirements Analysis
Quick screen shot of the board I am working on. It is a shield for a leonardo, but it has a Atmega328 (chosen for price point and ease of use) as "monitor" or low level brain to monitor voltage, control mosfets, a few basic sensors and be able to communicate with the leonardo by interupt and by serial.

Major features:
atmega 328
16x servo output via well documented ever popular TLC 5940
16x analog
5v regulator
3.3v regulator
3x mosfets
I want the option to mount my bt module directly to the pcb so you can see the footprint of the smd bt module outline.

(mostly unrouted because I am trying to get an idea of part placement and dimensions)


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05-13-2014, 11:38 PM
Post: #12
RE: Possible Shield Requirements Analysis
Looks good. Like the idea of this brain stem.

What is the PTC stand for and what is it doing?

What is the boost regulator doing? Is this a ready to by component?

I suggest a mosfet to kill the brain stem controller by itself if battery went to low. So you prevent it from destroying the batteries.

Rainer
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05-13-2014, 11:42 PM
Post: #13
RE: Possible Shield Requirements Analysis
(05-13-2014 11:38 PM)steamboat Wrote:  Looks good. Like the idea of this brain stem.

What is the PTC stand for and what is it doing?

What is the boost regulator doing? Is this a ready to by component?

I suggest a mosfet to kill the brain stem controller by itself if battery went to low. So you prevent it from destroying the batteries.

The ptc is a resettable fuse all arduino boards have them usually. I think this one cuts at 500ma.

I like the idea of added the mosfet, not sure how I missed that, But as a final shutdown step this is needed. I would like to be able to have the hardware be able to support logic where you can program the shellmo to slowly cut off power to various systems as the battery drains also. This would make shellmo lethargic when he has a dead battery...which could be a neat affect...
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05-13-2014, 11:46 PM
Post: #14
RE: Possible Shield Requirements Analysis
(05-13-2014 11:38 PM)steamboat Wrote:  What is the boost regulator doing? Is this a ready to by component?

The switching boost regulator that i have picked right now is the LTC3525. Its just a single chip. Its actually fairly expensive part (5us) because of its performance if we find a replacement thats cheaper thats fine, but I care more about performance in this parts since its the last to "turn off".

I am not comfortable running my arduinos unregulated and this will also allow us to get much more out of the batteries in a controlled safe manner IMO.
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05-13-2014, 11:52 PM
Post: #15
RE: Possible Shield Requirements Analysis
(05-13-2014 11:38 PM)steamboat Wrote:  I suggest a mosfet to kill the brain stem controller by itself if battery went to low. So you prevent it from destroying the batteries.

I think my thought process last night was if you kill the power at the 3 mosfets and turn off the 3.3v regulator and hist the 5v with a shutdown the 5v regulator is only going to leak 1μA which seems fine to me, adding another mosfet isn't a big deal either.
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05-14-2014, 12:01 AM (This post was last modified: 05-14-2014 12:07 AM by steamboat.)
Post: #16
RE: Possible Shield Requirements Analysis
(05-13-2014 11:52 PM)jmccartney Wrote:  5v regulator is only going to leak 1μA which seems fine to me
That is a fact! - so we don't need any more mosfets here. Maybe to kill the what ever "avakening sensor"?

I would suggest to couple the brain stem with the spinal nerves on one pcb to distribute the signals to the front, the end and the sides.

To speak technical please distribute the servo connectors at several sides of the pcb. This would make wiring a lot more easy.

Maybe we can include hall sensors for the leg motor revolution detection. Don't know much about hall sensors. We also could use reed relais and magnets...

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05-14-2014, 12:24 AM
Post: #17
RE: Possible Shield Requirements Analysis
(05-14-2014 12:01 AM)steamboat Wrote:  I would suggest to couple the brain stem with the spinal nerves on one pcb to distribute the signals to the front, the end and the sides.
HAHA. I knew you were going to say this. I will have to think very carefully, lots of traces to keep organized, but I agree, would be much more elegant than 16 servo connectors hanging off the one side.
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05-14-2014, 01:18 AM
Post: #18
RE: Possible Shield Requirements Analysis
(05-14-2014 12:24 AM)jmccartney Wrote:  than 16 servo connectors hanging off the one side.
But on other hand if we have "normal" user which want to use the servo wires as is, the wires would be long enough and has to be stored anyway. So don't mind about that point. We even don't know where which servo will be located.

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05-23-2014, 05:35 AM
Post: #19
RE: Possible Shield Requirements Analysis
So after getting some feedback I have been reworking the concept for a brain stem board. This is an updated screenshot of the very very general layout.

This is a Arduino Leonardo (though compatible with uno etc etc) shield design, its going to have an Atmega 328 for "brain stem" functionality and power/system control monitoring. It will also allow for 16 digital and 16 analog connections as well as at least 12* servo connections. I also hope to have two, but at least one pololu compatible motor driver socket Wink

Let me know your thoughts!


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05-23-2014, 06:59 AM (This post was last modified: 05-23-2014 07:36 AM by steamboat.)
Post: #20
RE: Possible Shield Requirements Analysis
Looks good for me. Great to have 4 ports for Servos and I/O pins including +5 Volt and ground this makes things much easier to connect.

What features have you planed for the power system? At least I woul like to see the voltage over BT on the Android.

My which would be (but not all which have to become true in live)
- an integrated BT module for all kind of Android communication.
- a temp sensor
- a real time clock chip with battery
- a gyroscope
- some kind of on/off or sleep button/functionality to keep shellmo alive for some days in sleep mode.
- a SD card slot for storing data and/or sending sound and music.
- an amplifier to play music
- an amplifier for a mic.

With this Shellmo could tell you how hot it was at home when you are coming back or at night. It could say hello. Could say good morning when it is time to get up or play your favorite music. It could try to walk straight ahead with the gyro.

All this could be added by shields but this would be space consuming, error-prone and not standardized - as more sensors are integrated on the shield as more people would use them and show others what and how to use it - but in general - I would like to have it ;-)

As ever all of this is a question of price. Maybe it is cheaper to buy this Chinese PCB'S for most of this functions and have sockets for them then to buy the bare chips and solder it onto the PCB.

Maybe the Gyro is not necessary because Shellmo will never go long distances - but on other hand this are fun features. I still have one of this as spare part for my quadrocopter Arducopter 2.6 but never used it in a land vehicle and even did not program it by myself...

So most of this are nothing else but dreams...

PS:
What about a camera?

Rainer
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