Pages: 1 [2] 3   Go Down
Author Topic: An Attiny85 I/O Network  (Read 2338 times)
0 Members and 1 Guest are viewing this topic.
Grand Blanc, MI, USA
Offline Offline
Faraday Member
**
Karma: 71
Posts: 3536
CODE is a mass noun and should not be used in the plural or with an indefinite article.
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Well, how many Attiny85's can I run on a single regulator without risking overheating it? Perhaps that is also an input question as well.

Depends on the regulator but in general, lots. At 5V and 8MHz, an ATtiny85 only draws 5mA. At 16MHz, 9mA. LEDs or whatever other loads are connected might actually account for the majority of the current.

If each board had a small regulator, rated for maybe 100mA, then they could maybe be used little more independently. When stacked they could be fed with 7-12V. OTOH, I don't see a lot wrong with one larger regulator feeding the whole stack, and that would cost less. Depends on what you want to do.
Logged

MCP79411/12 RTC ... "One Million Ohms" ATtiny kit ... available at http://www.tindie.com/stores/JChristensen/

Brisbane, Australia
Offline Offline
Edison Member
*
Karma: 29
Posts: 1074
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

What was the reason for multiplying the regulators?  How many ATTinies was that to run?
Well, how many Attiny85's can I run on a single regulator without risking overheating it? Perhaps that is also an input question as well.

I choose 4 regs., for 4 micro processors because it was a safe assumption and guaranteed all would be "fed" properly. I want all Attiny's to have an output of 4+v.
The ATTiny85 has 200mA as the absolute maximum current across VCC & GND pins (section 21.1 of the datasheet) so if you're using a basic LM7805 linear voltage regulator which can output 1.5A the answer is "at least 7".  In reality that is the absolute maximum consumption, which would be achieved when the output pins of the ATTiny are being used to source power (up to 40mA each) and wouldn't be where the uCs are comfortable operating for long periods.  As noted above, it would be preferable the LEDs are fed power directly and the ATTiny is used to control rather than power them.

I would expect one voltage regulator to have covered 4x ATTiny85 with lots of headroom.  The question of heat is a factor of what voltage you're regulating down from also.  The higher the input voltage, the higher the power that is converted to heat by the linear regulator.

Cheers ! Geoff
Logged

"There is no problem so bad you can't make it worse"
- retired astronaut Chris Hadfield

Pittsburgh, PA, USA
Offline Offline
Faraday Member
**
Karma: 58
Posts: 4036
I learn a bit every time I visit the forum.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

What was the reason for multiplying the regulators?  How many ATTinies was that to run?
Well, how many Attiny85's can I run on a single regulator without risking overheating it? Perhaps that is also an input question as well.

I choose 4 regs., for 4 micro processors because it was a safe assumption and guaranteed all would be "fed" properly. I want all Attiny's to have an output of 4+v.
The ATTiny85 has 200mA as the absolute maximum current across VCC & GND pins (section 21.1 of the datasheet) so if you're using a basic LM7805 linear voltage regulator which can output 1.5A the answer is "at least 7".  In reality that is the absolute maximum consumption, which would be achieved when the output pins of the ATTiny are being used to source power (up to 40mA each) and wouldn't be where the uCs are comfortable operating for long periods.  As noted above, it would be preferable the LEDs are fed power directly and the ATTiny is used to control rather than power them.

I would expect one voltage regulator to have covered 4x ATTiny85 with lots of headroom.  The question of heat is a factor of what voltage you're regulating down from also.  The higher the input voltage, the higher the power that is converted to heat by the linear regulator.

Cheers ! Geoff

The ideal would have leds and other loads not draw their operating power through the MCU's at all. That's what resistor-transistor pairs or driver chips are for.

My UNO has a regulator that gets -bypassed- when operating on USB power. It is only there for when I want to run from higher voltage sources which so far has been never. My Teensies don't have regulators at all and they work just fine.

You best choice is to make the regulators part of the power system. 3 Tiny's on a socket certainly don't call for 3 regulators. 3 bypass caps maybe but not 3 regulators.
Logged

Examples can be found in your IDE.

Global Moderator
Dallas
Offline Offline
Shannon Member
*****
Karma: 178
Posts: 12288
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
3 bypass caps maybe...

If you want analog-to-digital conversion to work there is no "maybe" about it.  ATtiny processors really truly need physically close bypass capacitors.
Logged

Pittsburgh, PA, USA
Offline Offline
Faraday Member
**
Karma: 58
Posts: 4036
I learn a bit every time I visit the forum.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
3 bypass caps maybe...

If you want analog-to-digital conversion to work there is no "maybe" about it.  ATtiny processors really truly need physically close bypass capacitors.


The right parts for the job. That's what we all need.
And EE-type Gurus to help us know them!

Logged

Examples can be found in your IDE.

Offline Offline
Newbie
*
Karma: 0
Posts: 38
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

You guys are something else! Thanks for all the help. That's great to hear the reg. situation can be simplified.

Back to square one I suppose.

I've got one other question if you don't mind. As for programming the boards, it would cost far more in resources to make a dedicated "ISP programming board". Trying to cut down on my budget and overall costs, couldn't I just add a 2x5 pin shroud to each board and use the USBasp ISP programmer? (Haven't tried out that programmer yet.)

Maybe its just me, but I don't like using the Arduino to program Attinys. Switching out chips back and forth and whatnot.
Logged

Brisbane, Australia
Offline Offline
Edison Member
*
Karma: 29
Posts: 1074
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

If swapping out the microcontroller to program it bugs you, there's always the option of putting a 6 pin header on your board and programming them in-place too.  If you add a dedicated programming board, are you thinking that would just be a set of headers and some kind of switch to select the target uC to program?  If so that sounds like headers on each uC level would be cheaper/simpler to me, but entirely your call of course.

Cheers !
Geoff
Logged

"There is no problem so bad you can't make it worse"
- retired astronaut Chris Hadfield

Pittsburgh, PA, USA
Offline Offline
Faraday Member
**
Karma: 58
Posts: 4036
I learn a bit every time I visit the forum.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

If you have lots of them, why not set up a ZIF socket and ISP circuit on a breadboard?
Then your modules wouldn't need headers either.

Another thing to give you mileage would be to use SPI shift-registers to light the leds and 1 Tiny to send data to many daisy-chained shift registers. A Tiny running at 8 MHz can send SPI data at 1 MBps or less which allows longer SPI bus lines but still you could change 40 8-bit registers 20,000 times a second with cycles to spare for another 6,214... which would give time to communicate with other Tinys on the same SPI bus.

I wouldn't bother with boards for something so simple, there's another buck apiece for many pieces. I like sockets, you can plug leads (headers too?) in the holes as easily as chips and either solder to the legs or push them into connectors. They're cheap and even cheaper in quantity, and a few extra pins don't hurt do they?

Well anyway, that's just stray thoughts.


Logged

Examples can be found in your IDE.

Offline Offline
Newbie
*
Karma: 0
Posts: 38
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

If swapping out the microcontroller to program it bugs you, there's always the option of putting a 6 pin header on your board and programming them in-place too.  If you add a dedicated programming board, are you thinking that would just be a set of headers and some kind of switch to select the target uC to program?  If so that sounds like headers on each uC level would be cheaper/simpler to me, but entirely your call of course.

Cheers !
Geoff

I know what I said before, but things change as new ideas develop.

Now, I pretty sure I would like all the boards made equal. But they will still have all the functionality as before. 

I think that is possible with the USBasp. Cuts down on: costs, overall work, wires and frees up my Arduino. The most practical solution I can see is simply adding a few male pins for the 5x2 native USBasp connection.

To be honest, I'm very unsure. New territory for me. So your input is very much appreciated.

____

On a side note, one thing I forgot was 10k pull-down required between signals. AH, that is going to be hard to incorporate. Probably have to use a DIP switch.
Logged

Brisbane, Australia
Offline Offline
Edison Member
*
Karma: 29
Posts: 1074
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

There is no wrong way in this choice (at least I don't think there is).  I'm working on a small board now with ATTiny where I'll have 60 made up - the first 10 prototypes arrived tonight in fact.  The programming for this one is unlikely to be often, so I'm going for a socketed ATTiny to cater for those occasions rather than soldering 60 sets of headers.  Colour me lazy maybe  smiley  In contrast, if you think these things will be programmed often I'd do what you're suggesting with the ICSP headers (or equivalent) for sure.

I've seen some designs using bare pads for the ICSP so a rig with pogo pins can be used for programming also.

It's good to see you're taking this one back on.  Do keep this thread updated.  Cheers !
Geoff
Logged

"There is no problem so bad you can't make it worse"
- retired astronaut Chris Hadfield

Pittsburgh, PA, USA
Offline Offline
Faraday Member
**
Karma: 58
Posts: 4036
I learn a bit every time I visit the forum.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

No wrong way sure. But if you ever get into manufacture you may find that market competition provides for product evolution. In this world it's survival of the cheapest in a bang for the buck manner. Function, lifetime, maintenance and running costs all factor into the bang but when the price is higher for less than the same overall increase or the thing will soon enough be obsolete then you've made a Tiger tank when you should have made a dozen T-34's. 

Logged

Examples can be found in your IDE.

Offline Offline
Newbie
*
Karma: 0
Posts: 38
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Trying to find a good solution for switch between the 5v USBasp ISP and the 5v-15v DC jack. I'm sure I can figure it out but if you have a simple solution I'm all ears.

One thing that is mind numbing, so currently I have a resistor on each I/O going "up" for the pull down. I'm curious if would it would be possible to use just a single resistor for all of them? But being their not all on at the same time, or if they were by chance. I don't know to even where to start with that formula. Maybe I could just calculate for them all to be on, and still get a good pull down result if only one is actually sending.
Logged

Pittsburgh, PA, USA
Offline Offline
Faraday Member
**
Karma: 58
Posts: 4036
I learn a bit every time I visit the forum.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Now, I pretty sure I would like all the boards made equal. But they will still have all the functionality as before.

Just trying to point out that 1 board can run many leds in different ways. 1 board per led is amazingly inefficient in terms of cost, materials and time. It even multiplies the number of chips you have to re-program with all that goes with that. For what you do, you don't really need boards, just something to hold parts together and attach to enclosure or mounting. A lot of things can be built right onto/into cabling.

I can get up to 32-pin narrow IC sockets for 15 cents each, maybe less in quantity.
http://www.futurlec.com/SockIC.shtml

I get small generic boards with hole pads and finger edges, they run over a buck each in 5 to 10.
 

Logged

Examples can be found in your IDE.

Offline Offline
Newbie
*
Karma: 0
Posts: 38
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Now, I pretty sure I would like all the boards made equal. But they will still have all the functionality as before.

Just trying to point out that 1 board can run many leds in different ways. 1 board per led is amazingly inefficient in terms of cost, materials and time. It even multiplies the number of chips you have to re-program with all that goes with that. For what you do, you don't really need boards, just something to hold parts together and attach to enclosure or mounting. A lot of things can be built right onto/into cabling.

I can get up to 32-pin narrow IC sockets for 15 cents each, maybe less in quantity.
http://www.futurlec.com/SockIC.shtml

I get small generic boards with hole pads and finger edges, they run over a buck each in 5 to 10.
 



Why would you buy an Arduino to run a single LED? As I explained how this could running LED's, that is isn't the only and intended purpose.

As of now, one Analog pin is connected to the on board LED. But all 5 Attiny85 I/O pins communicates up to the next board, as well as they all go outwards (no pull down) via headers if you wanted to use jumper wires to go out to a breadboard etc.

As for selling these, I only want to sell one or two sets to make my money back so I can throw back towards another project. There are many ways to skin a cat, these will be made on PCB's.
Logged

Offline Offline
Newbie
*
Karma: 0
Posts: 38
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I pray to the pcb layout gods this is the last base board I'll need to design for this project. And I couldn't find a way to make them all equal. Adding being I'm not going to manufacturer these now, I can use what double sided clad I have. Honestly I don't think its possible on single. . .

If it works I will not be making anymore changes. Fingers crossed, I'm going to start putting together the top boards.

(Excuse the bottom right route, I know its touching.)
Logged

Pages: 1 [2] 3   Go Up
Jump to: