OpenCircuits - User contributions [en]

24" Wall Clock

2008-07-16T10:06:07Z

122.213.250.14: calatrracr

letocodomace
{| align=right
|-
|
[[Image:Sign light Three 400x400.jpg|Light Sticks]]
|}
===Project Scope===
Description: Sometime ago a friend challenged us to build a 6 foot digital clock - just like the alarm clock next to your bed. Well, because of scaling issues, 6 foot was a bit too expensive. Instead, we are going with a 2 foot clock. I'm not entire sure about the end size, but you get the idea. And just to be geeky, let's use GPS to snag the time with 100ns accuracy.

The control system is fairly straight foward. Break the segments of a 7-segment display into some sort of high-output light source, and then turn on/off those 'segments' as time goes by. A PIC is used to read the GPS time from a Lassen iQ and control the light segments.

[[Image:LED7SEGLG 300.jpg|150px]]

Here is an example of the customary 7-segment display. We aren't going to copy this directly, but close.

We need to use something to illuminate each segment of the display. How about a light bar. What's a light bar? Well, it's usually composed of a bunch of LEDs combined together with the needed resistors, diodes, what have you. We could build our own, but I'm lazy and [[http://www.besthongkong.com/ Best Hong Kong]] has something called a ''Sign Light Module'' that looks like it could do the job really well, for only $2.39 a piece! That's cheaper than I can put a stick together, so I put 50pcs on order. We'll see how they look when they come in.

Here's the plan:

18:88 will be displayed worst case.
*Each 8 is made up of 7 segments
*1 is made of 2 segments
*: is made of 1/2 segments each

To make the clock slightly larger, we are going to use two light 'sticks' for each segment. Each stick looks like it's about 6" long, which will make a segment aprox. 12", which whill make the number height ~24" overall. Each dot in the ':' will be made out of one stick (6" tall). This may look a bit odd, only time will tell.

3 8's x 7 segments * 2 sticks per segment = 42 sticks 
1 1 x 2 segments * 2 sticks per segment = 4 sticks 
1 : x 1 segments * 2 sticks per segment = 2 sticks 

48 sticks needed overall 
Minimum of 23 inidividual control channels needed
----
===Power Regulation===
Quick math : Each stick is 3 LEDs. Each Piranha LED is 20mA according to the website (I don't trust the Hong Kong Website very much, but we'll assume). So each stick is 12V @ 60mA. 50 sticks * 60mA = 3A @ 12V. This is a bit juicy for a wall-wart. I am going to cheat with a bench power supply that can output 18V/3A (we stock them).

3A is really the worst case scenario. We only have 48 sticks (not 50) and 10:08 seems to be the real time with the most number of segments lit (44 sticks turned on). We obviously should never see a time of 18:88. At 10:08 we'll need 44 * 60mA = 2640mA = 2.6A. Not too horrendous.

The control board will need some power as well. 5V for logic, 3.3V for GPS. But the overall consumption will be peanuts compare to the lighting. Probably under 50mA for the control board.

----

===Clock Control===
Who wants to set the real time when we've got GPS to set it for us?! :) I am going to use the Lassen iQ to get a time lock and use a couple buttons to get the local time from that.

We need to control 23 channels 18:88:
*1 has two segments, but the entire number is either on or off
*: is always on, but we may way to flash it for seconds
*888 21 channels

I decided on 25 channels just in case I need some extra [[http://www.bullshitjob.com/officespace/ 'flare']]. Perhaps an alarm of sorts. 'Beer Time' alarm at 4:30pm? We've got to keep our options open...

The need for 25 I/O pushed me towards the PIC 16F877A:
*Easy to program (I've got a big code base)
*Has enough I/O
*It can be bootloaded!
*It's got an RTC (when you add an external 32.768kHz xtal)
*UART to read the incoming GPS NMEA from Lassen iQ

ToDo : It's possible to reduce the number of channels by multiplexing. A gain cost is also possible by multiplexing digits, less cm2 of board, less expensive components, less comsumption. 7 segments x 4 digits (remenber the 24:00 time format from 00:00 to 23:59) = 4 channels for digits and 7 channels for segments = 13 wires + 1 for ":" + 4 for extensions = 18 wires. Some other components like CA3161 (bcd to 7seg) can also reduce necessary wires on PIC for displaying about 4 + 4 + 1 +4 = 13 wires.
----

===Light Control===
Well if the PIC 16F877A has got the timing and control down, how exactly do we turn on/off the light stick?

Since the sticks only pull 60mA, we can use cheap BJT transistors. Let's go solid state! Many itty-bitty SOT-23 SMD BJTs can handle up to 1A with a max input of 40V. The maximum power output is 350mW though. Luckily, when forward biased, the MMBT2222 has around 0.5V drop.

So 60mA with 0.5V drop, we are looking at 30mW dissapation. That's atleast in theory. I'll believe it when I see it of course. For the time being, I'm going to assume this will work...

All I need is an NPN BJT for each channel:

[[Image:Clock-Channel.jpg]]

While this should work, it's going to leave a bunch of connections with one pin 'hot'. A better design would probably utilize a PNP connected to RAW. Ehh - no big deal.

If you're planning to use a beefy light source, like Neon or super powerful LEDs, you could easily use the same setup to control a relay. [[Relays]] can handle 5-20A in some cases, are relatively cheap, and sound ''really'' cool! The only problem is they are big. And for this project, we wanted a relatively small control board. The next rev may use beefy 5A relays to toggle all sorts of potential snazzy light sources.
----
===Board Layout===
The PIC is connected to 25 channels, the GPS, a couple buttons, and a status LED. Here's the current layout in all its random glory:

[[Image:Clock-Layout.jpg|500px]]

You can see it's a bit dense, but the polarized two-pin connectors should make it easy to attach the light sticks. Everything was SMD to ease the assembly as much as possible. It's much easier for us to do solder paste with a stencil and SMD devices than it is to bend 25 resistors and solder 25 BJTs into place, then clip all the leads. PTH is actually pretty time consuming. I digress...

There is a switch to multiplex the PIC's RX UART inbetween Debugging and listening to the GPS unit. Be sure to use Port 2 on the Lassen iQ if you want NMEA output (4800bps by default).
----

===Things to Improve===

Nothing at the moment. We have to wait for all the parts to come in. Should be about 4 weeks.

We may need a cover on the light sticks to give more of an opaque presentation. TBD.
----
===Documents===
[[Media:SFE-Wall-Clock.pdf|SFE Wall Clock Main Board Schematic]]

[[Media:SFE-Wall-Clock-Channels.pdf|Channel Control Schematic]]

Footprints: 
[[SFE_Footprint_Library|SFE Footprint Library]]

FP Name: All sorts of FPs used.

Supplier Info: 

Related Items: 

[[Category:Projects]]

OpenCircuits:Community portal

2008-07-10T17:55:55Z

122.213.250.14: cbocdarcd

vartrcac
Welcome to Open Circuits.
This is a good place to talk about Open Circuits, as a whole.

We have {{NUMBEROFARTICLES}} articles now. Yay!

== free digital TV converter box coupon ==

https://www.dtv2009.gov/

== Anti-Vandalism Bot ==

''moved to our page discussing [[Spam]].''

== electrical mailing lists ==
Yahoo claims they have
[http://dir.groups.yahoo.com/dir/Science/Engineering/Electrical 1,831 electrical engineering mailing lists].
What would be a good way of letting the people on those lists know about the Open Circuits wiki, without spamming them?
--[[User:DavidCary|DavidCary]] 13:30, 31 May 2006 (PDT)

* Publish cold fusion howto :-)
* Send one email/week and only once per list. And be on topic, listen carefully for responses.
[[User:Freqmax|Freqmax]] 16:24, 30 July 2007 (PDT)

== about Open Circuits ==
So, is there any connection between http://OpenCircuits.org/ , http://OpenCircuits.net/ , and this http://OpenCircuits.com/ wiki?
--[[User:DavidCary|DavidCary]] 23:47, 13 June 2006 (PDT)

No. There is no connection between any of http://opencircuits.com and the other websites listed.
[[User:Chazegh|Chazegh]] 02:55, 18 June 2006 (PDT)
== web rings ==
Document an original microcontroller project and join a PIC webring, or AVR webring. 20 June 2006

== audio electronics ==

Is there some other wiki for people to talk about audio electronics?
Or is this Open Circuits the best wiki for talking about things like
''"[http://analog.com/ Analog Devices] AN-221: The Alexander current-feedback audio power amplifier"'' by Mark Alexander
?

I think I would prefer to offload all the audio electronics controversies to some other wiki
(but which one?).
Still, it would be nice to have some "tips for high-power electronics" here.
I imagine that tips page would list the various quirks of high-power MOSFETs, BJTs, TRIACs, and IGBTs,
and (given a particular motor or speaker or other load)
how to select one over the others,
and various ways of working around those quirks.
--[[User:65.70.89.241|65.70.89.241]] 07:17, 10 August 2006 (PDT)

I just joined Open Circuits. I have been servicing and designing audio equipment for several years (Recording consoles a specialty) I hope you will have a section for audio electronics. I also work with video projection systems and theatrical lighting (stage struck at an early age) I play electric rock-blues guitar, so I also am interested in tube guitar amps (Marshall and Boogie). And there is a big difference in what a guitar player thinks an amp should do, and what a recording engineer wants an amp for. I think these are valid points for discussion.
I've also got an interest in power supplies (my experience is mostly with linear, but I've started learning about switching designs). In fact that brings me to my question, I have some regulator designs based on the 723 that I'd like to share. How do I go about doing that? I built a replacement for a console /- 18V @6A supply when I couldn't find the original regulator devices. I used 723s with external series pass devices. The unit has been working for close to 10 years now, so I think the design is worth sharing. Is anyone interested?

I also research discrete op amps like the Jensen 990. I've been working (on and off for years) on a clone of that using more modern, easily available parts and devices. Anyone else?
Finally, in response to the first entry in this section, I too read that application note in Analog Devices Audio/Video Reference Manual. My copy is dated 1992. I've repaired a lot of amplifiers, but haven't built any. If anyone else is hip to this amp I'd like to hear about it. It is a very unique design. I also like the A75 amp design from Nelson Pass and Norman Thagard, and the Leach Amp by Marshall Leach. The last two are pretty normal as far as design goes, not as adventurous as the Alexander with its current-feedback approach.
Aloha, RAF--[[User:66.8.194.185|66.8.194.185]] 14:04, 18 May 2007 (PDT)

== automotive electronics ==

Is there some other wiki for people to talk about automobile electronics?
Or is this Open Circuits the best wiki for talking about things like
[http://megamanual.com/ "experimental Do-It-Yourself programmable electronic fuel injection controller"]?
Or should we just point people who want to talk ECUs (engine control units) to the
[http://msefi.com/ MSEFI discussion forum],
even though it sadly lacks a wiki?
--[[User:DavidCary|DavidCary]] 22:36, 2 July 2007 (PDT)

== inviting bloggers to open circuits ==

=== how to connect a JTAG probe to a Nokia phone ===

I'd like to invite bloggers such as GyrosGeier to edit OpenCircuits.
Rather than just spamming him, I think he would be more inclined to help out
if we answered one of his questions first -- such as
[http://hogyros.de/?q=node/167 "If you have information on how to connect a JTAG probe to a Nokia phone, please let me know."]
Maybe I should start a page on [[JTAG]]...
--[[User:DavidCary|DavidCary]] 09:37, 22 September 2006 (PDT)

The [http://hackedgadgets.com/ Hacked Gadgets blog also has a bunch of cool electronics].
--[[User:DavidCary|DavidCary]] 11:58, 5 January 2007 (PST)

== red links ==

The default skin at OpenCircuits currently has "red links" = page exists, "dark red links" = page does not exist.

I find that confusing. (But not as bad as the wiki that has some links black-on-white, indistinguishable from normal text).

'''work-around''': Register (it's free, and you don't have to give any personal information), then choose the "preferences" link in the far upper-right corner and then pick any other skin.

The other skins have coloring that you may be more used to from other wiki: "blue links" = page exists, "red links" = page does not exist.

--[[User:DavidCary|DavidCary]] 08:58, 18 December 2006 (PST)

*** Guys, the red color on links is AwuFul, it brings ppl headaches.
That's the only reason I cant participate ***

--[[User:Takeda|Takeda]] 16:38, 29 September 2007 (PDT)

== inviting people from other forums to open circuits ==

Lots of people talk about circuits for LED lighting at
http://candlepowerforums.com/
.
Perhaps we can talk some of them into contributing here -- perhaps using a page or two of Open Circuits as a FAQ for LEDs and drive circuits.

== tool lists ==

Should we have an entire page on "tools", and mention it on the main page?
That risks listing *every* tool anyone has ever heard about,
like the page at
http://massmind.org/techref/tools.htm
.
Yes, I'm responsible for uglier bits on that page;
I think the wide variety of oscilloscopes are particularly confusing.
How could we cut through the confusion?

I see the "techniques" page already has a list of software tools.
Perhaps it would be nifty to have a short list of all the tools necessary for each technique?
Then a beginner would have a better idea of what tools he really needs to get (rather than looking at a huge list of every tool, and wondering for each one, ''"Am I going to regret buying it when I see it gathering dust? Or am I going to regret not buying it when I need it during a midnight debug session?"'').

--[[User:DavidCary|DavidCary]] 08:37, 24 January 2007 (PST)

== Requests For Help ==
Thanks for your help with the camcorder mic.

== sample component ==

What is the purpose of the [[Sample Component]] ?
--[[User:DavidCary|DavidCary]] 16:27, 7 May 2007 (PDT)

----

== current surge and battery life ==

Hi,

currently my board is using a 3V battery, in every 40msec it will turn on its RF to communicate with the base station. I face a problem here is that my battery life is badly affected. Turning on the RF with cause a current surge.

Will this surge affect my battery life? If I use a supercapacitor does it helps?

-- [[User:203.120.164.208]] 04:14, 30 April 2007

== MIDI electrical interface ==

In my opinion, the MIDI interface got a lot of things right that too many later interfaces still trip over.

* http://www.repairfaq.org/filipg/LINK/F_MIDI.html -- ASCII schematics
* http://www.engadget.com/2005/08/30/how-to-control-csound-with-a-custom-midi-controller-hardware/ -- hand-sketched schematics
* http://www.midi.org/about-midi/electrical.shtml "MIDI Electrical Specification Diagram & Proper Design of Joystick/MIDI Adapters" -- well-drawn schematics
* [http://en.wikipedia.org/wiki/The_MIDI_1.0_Protocol Wikipedia: The MIDI 1.0 Protocol]
* http://en.wikibooks.org/wiki/Behringer_FCB1010_MIDI_Pedal

It may look simple, but too often people try to "improve" it by adding or removing things without understanding, ending up with a worse system.

Is there any other wiki that is more appropriate for explaining the low-level details of the MIDI electrical interface, and *why* it was done that way?

I would be most interested in discussing new communication interfaces -- but is this really the right wiki?
Or would http://en.wikibooks.org/wiki/Serial_Programming or the [http://interwiki.sourceforge.net/cgi-bin/picawiki.pl/StartingPoint PICA wiki] be better for discussing improvements?
--[[User:DavidCary|DavidCary]] 13:21, 21 June 2007 (PDT)

== IC design ==

What do you think about
http://makeyourownchip.com/
?
Should we talk about VLSI design ([http://david.carybros.com/html/vlsi.html "VLSI: designing electronic chips"])
here at Open Circuits?
Or is there a more appropriate wiki somewhere else?
--[[User:DavidCary|DavidCary]] 15:59, 26 June 2007 (PDT)

== electronics infoline ==

So have you seen
"Free electronics projects"
http://electronicsinfoline.com/
"with Photo Preview"
?
--[[User:DavidCary|DavidCary]] 00:28, 1 July 2007 (PDT)

== generating a netlist with a "C++" program ==

The [http://positron.ps.uci.edu/~pier/csc/sup/Support.html "Support Electronics for ATLAS Muon CSC"] documentation claims that [http://positron.ps.uci.edu/~pier/csc/sup/CRB_LayoutNotes0.pdf "The design was captured with C++. There are no schematics."] and lists [http://positron.ps.uci.edu/~pier/csc/sup/crb_srce the C++ source code].

How did they do that?
--[[User:DavidCary|DavidCary]] 01:15, 3 July 2007 (PDT)

== rocket electronics ==

Is there another wiki that talks about rocket electronics?
Or is this Open Circuits the best place to talk about
ground support electronics
(such as [http://www.ukrocketman.com/rocketry/controller.shtml Launch Controller]s)
and
onboard electronics
(such as one
[http://www.ukrocketman.com/rocketry/compactrdasguide.shtml flight computer]
or another
[http://david.carybros.com/html/schematic.html#flight_computer flight computer]
)?
--[[User:DavidCary|DavidCary]] 14:21, 15 July 2007 (PDT)

== Minimig ==
I have created pages about the [[Minimig]] project which is running an Amiga 500 in a Xilinx FPGA. It's rather a work in progress, than a static documentation. I hope nobody minds. [[User:Freqmax|Freqmax]] 18:35, 27 July 2007 (PDT)

== Open Science ==

So does/should Open Science ( http://openscience.org/ ) have any relation to Open Circuits ?
--[[User:68.0.120.35|68.0.120.35]] 00:13, 5 August 2007 (PDT)

== LaTEX math markup ==

I wrote a quick howto on figuring out resistor values, but it looks bad without latex math markup enabled.
Here's what I wrote as it appears on open circuits: http://www.opencircuits.com/Talk:Relays
Here's how it appears on wikipedia (with math markup enabled): http://en.wikipedia.org/wiki/User:Mzandrew/Sandbox

Anyone know if this is a quick thing to enable for open circuits or if it's involved?

[[User:Mzandrew|Mzandrew]] 14:16, 8 September 2007 (PDT)

<div style="clear:both;border:1px dotted #333;padding:10px;background:#FFE400;color:#333;margin-top:10px;margin-bottom:10px;">DONE! -- [[User:Chazegh|Chazegh]] 00:10, 11 March 2008 (PDT)</div>

----

'''SPAM DELETED!'''

I deleted a whole bunch of links that had been placed at the top of this page, probably by the same AH that did it to my page. I think the best solution would be to make it so no edits are possible without being logged in. Then there will be a record of who does this kind of thing. Then they can be banned from the site. I don't think that defeats the purpose of an open wiki environment, it simply means you have to register to contribute.

--[[User:RogerAF|RAF]] 10:30, 21 December 2007 (PST)

At least this page is still OK. The Spam AHole hit my user talk page again today. This is very aggravating.

--[[User:RogerAF|RAF]] 06:54, 22 December 2007 (PST)

: ''I agree. Annoying. I'm starting to "semi-protect" most pages so they can only be edited by logged-in users. I'm leaving a couple of pages wide open as a honeypot and/or test pages, so I can make tests and ban spammers without touching good pages. I think the $wgSpamRegex and/or ReCAPTCHA would be a better way to deal with spam. But my attempt to set them up isn't working yet. Sorry. --[[User:DavidCary|DavidCary]] 10:28, 3 January 2008 (PST)''

== Release 2.0 ==

[http://radar.oreilly.com/archives/2007/12/new_release_20_3.html New Release 2.0: Open Source Hardware] by Jimmy Guterman

Does Guterman know about Open Circuits yet?
--[[User:DavidCary|DavidCary]] 01:04, 4 January 2008 (PST)

== tech-assist ==

Should we invite the nice people at tech-assist
http://tech-assist.org/
to use the Open Circuits wiki?
--[[User:DavidCary|DavidCary]] 20:38, 15 January 2008 (PST)

== A post I left at the Schmartboard mailing list. ==

Last week I posted to the Schmartboard mailing list asking about more interface types for their system.
I made reference to sites like this and pleaded the case of individuals wishing to make projects that interface a little better than the methods available now. Neal Greenburg(VP in sales) replied that they had been kicking ideas around like what I was proposing for a while, and that he would like to get some feedback. So, if you're interested, head on over and pipe in. The basic request I made was asking for common internal pc interfaces(PCI, PCI-e, AGP, ISA, etc..) to be included as an attachable module.

The reason for my request was that this would allow organizations such as this one to develop hardware that is now unachievable at a decent prototyping price(quantities in the single digits). Their modules allow robust SMD hardware to be hand soldered and connected to other modules, but interfacing to a pc or other system is limited to rs232. I left a much more in depth post there, and if you're interested, you can find it there.

http://tech.groups.yahoo.com/group/schmartboardsv/

I'm not affiliated with schmartboard in any other way than as a customer. I'm sorry if this is seen as spam, it's not intended to be. If the general consensus is that this is spam, feel free to delete it.

Thanks for your time, take care.
[[User:Jonkopp|Jonkopp]] 13:49, 20 January 2008 (PST)

== open source machine ==

Is there some other wiki somewhere that would be better for discussing "open source hardware designs" for non-electronic mechanical hardware, such as
http://opensourcemachine.org/
?
--[[User:DavidCary|DavidCary]] 05:52, 26 June 2008 (PDT)

== confused ==

What is up with
[[User talk:Sunnyhouselife]], [[User talk:Kaylee]], [[User talk:Seekic]]
?
I'm guessing that English is not their native language.
--[[User:DavidCary|DavidCary]] 08:08, 10 July 2008 (PDT)