Placing an order for a Power Supply

rjo_

Dear Friends,

Skipping ahead a little; only two things stand between me and my self-assembling Propeller based prime number generator. A pick and place robot, with two nimble fingers on each hand... ( I can wait for this[noparse]:)[/noparse] AND

A power supply that I can easily plug 64 props into.

That (to me) sounds like an engineering challenge.

Rich

Mike Green

Step 1: How much power do you need? What voltages? How much current at each voltage?

Step 2: Have a look at the Jameco (or Digikey or Mouser or ...) catalog under power supplies.

Step 3: Find the power supply (or power supplies if you need more than one voltage and you don't want/need a multiple output supply) with the current output that you need.

Step 4: Order it and install it when it arrives.

How much of a challenge is that?

If you want to make your own from scratch, start with Step 1 and a good basic guide on power supply design. The Amateur Radio Handbook usually has a chapter on this. Check your local library for a copy.

One Propeller going full bore should draw less than 100ma by itself and the chip itself is rated to draw no more than 300ma. Say you have a maximum of 250ma per Propeller. That's 16A at 3.3V. Jameco has a nice looking 3.3V, 22A switching supply for $80. If you want a little 5V for "special logic", there's another supply with only 13A at 3.3V, but a second output at 5V (and a 12V output as well). This one also goes for about $80.

OK, you can wait for the pick and place robot. You don't have to wait for more than a few days for a ready-to-go power supply. What's keeping you?

Post Edited (Mike Green) : 11/5/2007 3:27:41 PM GMT

Mike Green

How about an 8 x 8 array of uOLED-96-Props, each with its own uSD card, built up as a nice visual matrix. That's about 20cm x 28cm. You could have one more off to the side to serve as a master controller with some 74HC138s for controlling the reset lines and some RS485 buffers. There would be 64 reset lines and 64 transmit enable lines, one pair from each uOLED-96-Prop. All Props would receive the same thing from the master. You'd need 2 sets of 9 of the 74HC138s to select 2 x 1 of 64 lines and you'd need 7 or 8 control lines for each set which you could do with either I2C I/O expanders or 74HC595 Serial Shift Registers.

You could lay out the motherboard pretty easily and populate it pretty cheaply with the control logic. You'd start with the master Prop and one slave Prop. Since the uOLED-96-Props are plug-in, you could just add them as you can afford it.

Each Prop would be connected to the adjacent Props in the matrix .. both horizontally and vertically ... that's 4 I/O pins ... and the edges of the matrix would connect around so any Prop would only be 3 stops away from any other. The programming I/O pins would be used to talk to the "master".

Post Edited (Mike Green) : 11/5/2007 3:53:23 PM GMT

rjo_

Mike,

Last question first: It's all a matter of focus. I have a lot to learn and there is no short cut.

Steps 1- 4... you might be right. Maybe what I'm asking for is a 64 way cable[noparse]:)[/noparse]

I want something slick. If I did it, "it" wouldn't be very slick. There are all kinds of guys, who have spent years perfecting their skills... I think there is a market for an adorable multiple power supply... or alternatively for a really sharp adapter for an existing power supply.

In the back of my mind it seems like there are all kinds of issues that get resolved at the board level with the Prop... handling some of those issues in an dedicated power supply makes intuitive sense to me... but that doesn't mean that it actually makes engineering sense.

"If you want to make one from scratch"... absolutely not... I haven't even finished my coil winder yet@!@!!!

The other issue that will have to be addressed is "being able to conveniently program multiple Props from the IDE," which doesn't absolutely have to be done, but it sure would be nice. IDE issues are getting toward the front burner... I'm hoping that this issue gets attention.


Rich

rjo_

Mike,

I have powered multiple props... just by daisey chaining from a 9 volt RadioShack power supply... but I always get the feeling that even though it works, it can't be the right way to do it.

Rich

Mike Green

If you wanted to use the uOLED-96-Prop as I suggested, you would need a 5V distribution system and a 5V power supply since each uOLED-96-Prop has its own local 3.3V regulator. If you used a mother board setup, you'd have a ground plane on one side of the board and much of the copper on the other side would carry the +5V. You'd need a 0.1uF ceramic and probably 10uF electrolytic at the connector for each uOLED-96-Prop as well as a 0.1uF capacitor at each RS485 driver.

If you don't use a motherboard setup, you'd probably use a bus-strip. You'd get a couple of terminal blocks, maybe two strips of 16 each or two strips of 8 each with all the terminals on a strip connected together with heavy wire like 14 or 16 gauge and that would be connected to the power supply. Each terminal pair would run using a length of 18 to 22 gauge wire to maybe 4 or as many as 8 Propellers. The trick is to keep the current in each line low enough so you don't get much voltage drop through the wire.

rjo_

Mike

I absolutely intend to use multiple uOLEDs, little clusters of them[noparse]:)[/noparse] AND they have the memory that I need right on every little uOLED. Amazing.

About the USB issue... I'm lobbying for a combo development of a smart USB switch and an IDE, which can be told that the switch is there. The ide also has to be able to keep a laundry list.

Thank you so much.

Rich

Mike Green

I think you'd be better off with a master Propeller that has a switch or jumper that either connects the DTR line from a USB to Serial adapter to the Reset pin or to an I/O pin and has a special downloader/control program that would let you download a program using the Propeller Tool, but to an SD card. You could even control this with a 4x4 keypad or a PS/2 keyboard.

By the way, could you rename this thread to something like "Power Supplies or Supercomputer Revisited"?

rjo_

Mike, Mike, Mike,

Re: "By the way..."

I don't know how.

Re: "I think you'd..."

I know the basic capabilities of SD cards, but that's about it for the moment. Another good reason to order my first uOLED, huh?

"that would let you download a program using the Propeller Tool, but to an SD card..."

You would do that for little old me?

Rich

Paul Baker

rjo_ said...
Mike, Mike, Mike,

Re: "By the way..."

I don't know how.


Rich

Click the pencil icon in the upper-right of the top post, you can edit the subject line in the box for it. (you can edit any post of yours by clicking the pencil icon of the post).

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Mike Green

Rich,
It's not convenient, but you can manually do this (download to SD card files) already:

1) Download the program you want to EEPROM using either the Propeller Tool or PropTerminal

2) Download a copy of DongleBasic to RAM

3) Start a copy of PropTerminal if not already running

4) Use the COPY [noparse][[/noparse]0],"<file>" to copy the contents of the boot EEPROM to the specified file

5) Repeat as needed

There's already a Spin Loader that Chip wrote that runs on one Propeller and downloads a program to another.
You'd have to modify it to download from an EEPROM or an SD card (and to handle selecting the particular Prop to download).

rjo_

Mike,

Sorry for the delay... I had to run over to Radioshack to pick up a couple of nF capacitors[noparse]:)[/noparse]

I had the general approach, but seeing the specifics in black and white and coming from you is very helpful.

There is certainly enough available so that I can put together develop a proof, but then I would still have to go through an additional design iteration. BUT since this is a hardware and a software development, AND SINCE I don't want to throw anything out, your answers are perfect in the sense that I don't have to do anything now that I will wish I had done differently later.

As a general principle multi-Prop programming is going to require automation in the IDE. Let's say a guy wants to build systems in his garage and he wants to be able to specify... "this code goes to Prop 1 RAM and that code goes to Prop 2 RAM and the other code goes to Props 3 - 64 EEPROM." And he doesn't want to do it all by hand. The IDE should allow for a single set up... and then it should be just a matter of plugging everything in an hitting a button and waiting for a fatal error report.

No doubt there has to be something like a configurable USB switch in between everything... which seems like it should be built around a Propeller, which would make it one heck of a smart switch.

Thanks again.

Rich

PS... I would love to play like a journalist and interview you for the other guys on the forum. It is truly wonderful to have you participating here... what do you say?
I would have asked you privately... but I was afraid you'd turn me down[noparse]:)[/noparse] We could do it off line first and make it subject to your complete approval.