Propeller Robot PCB work in progress.

Bits · 2012-07-30 10:25

Okay here is a schematic of a Robot PCB I am working on. Please comment on features that would be neat to add but keep in mind that this should be inexpensive.

Its incomplete at the moment.

The first picture is power management with one sensor input (sonic). Its using two switcher regulators with the option to turn on and off the 5V rail. The schematic below contains memory, and propeller.
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Oldbitcollector (Jeff) · 2012-07-30 10:34

Nice!

Question, what program did you do that beautiful schematic in?

Jeff

Bits · 2012-07-30 10:40

I use national instruments Multisims.

Phil Pilgrim (PhiPi) · 2012-07-30 10:45

Pullups should be at most 10K -- especially R9 and R10 -- 4.7K preferred. Add pullups to P30 and P31. You show only one Vdd and Gnd connection to the Prop. You need to connect all four pairs.

-Phil

Bits · 2012-07-30 10:51

Ah I guess its not shown but there are connections to the other 3 Vdd and 3 Grounds (internal connected).

As for the 4.7K Ill make that change. Thanks.

Oh just thinking out loud that the boys I bring over for a glass of wine are going to freak out when my robot runs around my living quarters.
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ratronic · 2012-07-30 11:22

Bits the internal connection's need to be wired to VDD and ground externally.

Bits · 2012-07-30 11:40

ratronic they are its just the way I molded the propeller part.

Here is an optional H-bridge circuit. The control pins are not connected to the propeller yet, so keep that in mind. One thing I wonder about is the switching speed that the TLP190B can handle.

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Phil Pilgrim (PhiPi) · 2012-07-30 11:47

Bits,

Be sure to read the TLP190B datasheet. It looks like the smallest load resistor that it's characterized for is 300K. You won't get close to a significant gate drive with a 10K pull-down to the source. Also, the turn-on and turn-off times are very slow, so don't count on being able to PWM the H-bridge with this configuration.

BTW, with a proper layout, you don't need optos on the low side, so you could replace them with faster drivers that you can PWM.

-Phil

Bits · 2012-07-30 12:00

Ergh!

Thanks Phil, I will look into a different IC. Now I see the on and off times (1ms Off and .2 ms On).

prof_braino · 2012-07-30 12:17

I like this.

I see there's a shutdown on the regulator pin 1 connected to P27. Data sheet says low enable, and there's a pull up. So does this mean that the prop holds the line down, and if it lets go, the regulator turns off? That's kind of cool.

Does there need to be a switch or something to bring it low so the prop can start in the first place? Or does it just restart right away?

Can there also be a kill switch wired in there too? Just in case...

Edit .. now I see. I thought the 5v was feeding the 3.3v. Now I see Vp means both are connected to the power supply. I'll learn this yet. So we can turn off the 5v via software. OK, even cooler!

Bits · 2012-07-30 12:28

prof_braino wrote: »

I like this.

I see there's a shutdown on the regulator pin 1 connected to P27. Data sheet says low enable, and there's a pull up. So does this mean that the prop holds the line down, and if it lets go, the regulator turns off? That's kind of cool.

Does there need to be a switch or something to bring it low so the prop can start in the first place? Or does it just restart right away?

Can there also be a kill switch wired in there too? Just in case...

Well my thought was to be able to turn on and off the 5volt rail using the propeller pin to conserve power when needed. The 3.3V rail is always on so that the propeller can run. The pull up is so that the 5V rail is never left floating. I don't think a switch will be needed unless there becomes a need for more pins on the prop.

Bits · 2012-07-30 12:36

Phil, others what about this IC for motor and stepper motor control. This might be a cool solution to kill 2 birds with one stone!

[h=1]TC4469COE713[/h]
I cant see many disadvantages right off hand.

Phil Pilgrim (PhiPi) · 2012-07-30 12:55

Bits,

You can't use that chip to drive the NMOS transistors in the high side; you'd have to replace them with PMOS. You can still use the optos on the high side and a regular nMOSFET drivers on the low side. You do not need to PWM both the high and low sides: just the low side.

One thing to be very wary of, though, is "shoot-through." If the low side transistor on one side turns on before the high-side transistor on that side turns off, it will destroy the H-bridge. H-bridge ICs typically have delays built-in to keep this from happening. And don't plan on the delays being provided by software. One software glitch, and poof!

-Phil

idbruce · 2012-07-30 12:58

Looks like a pretty nice chip to me. I will save that datasheet.

Thanks Bits

Bruce

Bits · 2012-07-30 13:04

Phil Pilgrim (PhiPi) wrote: »

Bits,

You can't use that chip to drive the NMOS transistors in the high side; you'd have to replace them with PMOS. You can still use the optos on the high side and a regular nMOSFET drivers on the low side. You do not need to PWM both the high and low sides: just the low side.

One thing to be very wary of, though, is "shoot-through." If the low side transistor on one side turns on before the high-side transistor on that side turns off, it will destroy the H-bridge. H-bridge ICs typically have delays built-in to keep this from happening. And don't plan on the delays being provided by software. One software glitch, and poof!

-Phil

Yea great point, so I need to install a delay. I actually don't mind using a p-chan on the high side and I can drive stepper motors as well with one ic.

Bruce
Thanks, it does seem like a nice IC. We will see.

idbruce · 2012-07-30 13:11

@Bits

I am sure the A3988 has been around for a while, but I have never seen it before today. It is a Quad DMOS Full Bridge PWM Motor Driver capable running two bipolar steppers. From the datasheet, it looks like a very simple and plain setup for two bipolar steppers.

General Information: http://www.allegromicro.com/Products/Motor-Driver-And-Interface-ICs/Bipolar-Stepper-Motor-Drivers/A3988.aspx

Datasheet: http://www.allegromicro.com/Products/Motor-Driver-And-Interface-ICs/Bipolar-Stepper-Motor-Drivers/~/media/Files/Datasheets/A3988-Datasheet.ashx

Bits · 2012-07-30 13:34

Yes I have seen this IC and honestly I shy away from Allegro parts. I just have bad luck with them besides the A3988 consumes a lot of prop pins.

Bits · 2012-07-31 10:50

Today I have made some changes and included a few extra features.

1 Blue tooth communications
1 5V precision reference regulator for measuring with a 16 bit ADC
1 Humidity sensor
1 Temperature sensor
1 GPS
1 Alarm switch
2 Sharp Optical distance sensors
1 Ultra sonic module
1 SD memory slot

I was wondering if anyone has used Bluetooth to transmit voice and sound? Also is there a speech IC that I can use as well to make a robot voice? I have 5 more channels for Analog sensor input so ideas are welcome. I am on the fence with a display I think it would make debugging easy but then again there is USB.

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erco · 2012-07-31 13:26

@bits: Have you prototyped anything yet? You have an interesting array of parts & sensors there, I'm curious if you have any specific function or goal in mind.

Bits · 2012-07-31 14:06

Funny you mention this because I am prototyping and testing it now.

Switching PS. ✔
VNH3SP30TR-E ✔
MCP23016 ✔
LT1460 ✔
ADS8345 ✔
GP2Y0D21YK0F ✔
Temperature ✔
Alarm ( very loud) ✔
LMX9838 ✔

Things I have not check as of yet are:

[FONT=arial, helvetica, clean, sans-serif]Humidity - need to order still. [/FONT]
[FONT=arial, helvetica, clean, sans-serif]SD card - need to order it as well
[/FONT]Servos - need to test. I want to run them through the I/O expander (MCP23016) but think that it might be to slow.

[FONT=arial, helvetica, clean, sans-serif]My goal is to build a robot PCB but this prototype is overkill at the moment, just for me

. Ill remove blocks of circuits when directed by others to make things simpler for them. I am going to make 10 or so PCBs once its all said and done. Want one? [/FONT]

[FONT=arial, helvetica, clean, sans-serif]Some things I want to add are Sound and Voice via BlueTooth [/FONT][FONT=arial, helvetica, clean, sans-serif]( [/FONT]LMX9838 )[FONT=arial, helvetica, clean, sans-serif] . The IC [/FONT][FONT=arial, helvetica, clean, sans-serif]I have selected contains features with the help of a few additional parts will make it possible. Currently I have wireless range of ~ 9 meters. I wonder if 5V would increase this distance?

[/FONT]I also want to add more things to the PCB but drawing a blank at this posting. Any ideas? Let me know.

erco · 2012-07-31 15:33

On an indoor mobile robot, navigation is everything. You'll likely want motor or wheel encoder input (quad encoders will require 4 inputs total), and probably more than one ultrasonic sensor. The MadeUSA uses 8 at a time. That's great news for the Parallax store.

If I may be so bold to suggest, you may also want a few directional IR receivers to navigate between IR beacons. I'm tackling that naughty problem right now at home on a small robot.

When in doubt, leave open headers and let the user customize to their application. I'd rather have an open header than a built-in humidity module, but that's just me here in low-humidity Los Angeles.

Bits · 2012-08-01 07:11

Thanks erco this is perfect. I cant believe I forgot the encoders. Time to get to work.

Propeller Robot PCB work in progress.

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