OpenCircuits - User contributions [en]

24" Wall Clock

2007-06-24T11:12:06Z

163.192.3.146: /* Project Scope */

{| align=right
|-
|
[[Image:Sign light Three 400x400.jpg|Light Sticks]]
|}
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===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]]

Programmable Chip EEG

2007-06-24T09:03:07Z

163.192.3.146: /* See also: */

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== Status ==
We currently have a (preliminary?) [[circuit design]] and a (prelimary) [[PCB layout]].
We are using LT switcher CAD to draw the scematic.

== Hardware Overview ==
Here is a diagram of how the analog signal processing boards and the microprocessor board will come together.
[[Image:Pceeg.jpg]]
Here is how the analog signal prossesing board will come together.
[[Image:newpceeghddesign.png]]

==ESD Protection in 1168 and Max3235E ==
Chips have been chosen that fallow the human body model of esd protection this can be seen in the 1168 and Max3235E datasheet.

== Description of How it Works ==
The daughter signal prossesing board is responcible for filtering and digitising the signals from the body, then the signals are passed to the control board that is the motherboard. The motherboard then can pass the signal to a larger computer.

The differential analog signal is amplified by the instramentation amplifier. Then the signal is amplified and conditioned by high pass and low pass filters.

The common mode signal is inverted summed and sent back to the body to decrese common mode signal thsi is done by the driver right leg circuit.

Band reject filters may be added soon in the future.

Then the analog signals are simultaniously digitized and the digital values can be clocked to the controler motherboard.

The controler board that is the mother board of the system and the signal prossesing daughter boards plug into is the [http://en.wikipedia.org/wiki/AVR_Butterfly AVR Butterfly]

=== How You Can Help ===
#. get the tools
== Software Tools ==
* We are using LT switcher CAD to draw the scematic. This also is a SPICE Simulator used to analize the amplifier design.
* Eagle CAD could be used in the future after all the parts are surface mount & the analog sections are alalised. To autorout future designs.
* Express PCB is being used to create the first PCB but surface mount must be used to save hole count and space.
* Maxima a computer algebra system s used for graphing and matth displays.

*[[I2C]] interface diagram for programmable resistors and a/d converters 12 or more bits with low cost.
*SPI interface diagram for programmable resistors and a/d converters 12 or more bits with low cost.
*linear switcher cad schematic drawing from PCEEG technology applied to the Open EEG design with improvements.
*migrate from switcher cad to pcb express.
*migrate from pcb express to eagle cad after testing to further development.

== Parts used in the PCEEG: ==
* [http://opencircuits.com/LT1168 LT1168 Programmable-Gain Precision Instrumentation Amplifier] is used to amplify the weak electric signals coming from the brain through electrodes attached to the scalp, etc.
* Several [http://opencircuits.com/LT1114 LT1114 Low Power Precision OP-Amps] are used for amplification and filtering of the signal
* The [http://opencircuits.com/Digitally_Programmable_Potentiometers Digitally Programmable Potentiometers AD5204] 4-Channel Digitally Controlled Potentiometer is used to make calibration of this device easier. (Historically, a weak point of homebrew designs has been their sensitivity to component value; tolerance and drift have made them require constant tweaking for good results.)

To reduce noise in the readout of the analog part of this circuit, a common-mode feedback is passed back into the body by the driver right leg circuit. Band reject filter may also be used (to reject, for example, 60Hz noise from nearby A/C power wiring).

The analog signal prossesing board will digitise the signal and pass the data to the control board. The control board is based on the [http://en.wikipedia.org/wiki/AVR_Butterfly AVR Butterfly] which will, further process the signals, and provide an interface to a computer & lcd display.

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== Open Source Circuit Design ==
* [http://opencircuits.com/Programmable_Chip_EEG Open Source Circuit Design ]
* [http://www.thinkcycle.org/ Think Cycle]
* [http://pceegbci.blog.com/ The Programmable Chip EEG Open Source Circuit Design BLog]

== Open source (public) results! ==
PHP will be used to create a database of users and what they sample and choose to share with the open source community.

The database will give statistical analysis on users recordings.

Also the extension of SETI called BIONIC could be used as a distributed library creation of artifacts and data mining.

Please contribute and make the PCEEG a great tool for researching brain computer interfaces.

== A/D Converters ==

The programmable chip EEG needs an A/D converter to convert the analog signal (at the output of the instrumentation amplifier) into digital bits.
We expect this project to require at least 20 bit ADC.

The ads1255 by ti is a great a2d converter it has programmable gain and digital low pass filtering with 24 bits of resolution 30KSPS.

It is a 20-SSOP so it might be able to be soldered by a hotplate or hot air rework tool.

Many Atmel and other microcontrollers have a built-in ADC, but those are at most 10 bit ADC, so that ADC is useless to us -- we are forced to use an external ADC.

What low-cost ADC are available with at least 12 bits?

* $2.50 MCP3301 has 1 ADC input (13 bits)
* $3.50 MCP3302 has 2 ADC input (13 bits)
* $3.50 MCP3204 has 4 ADC input (12 bits)
* $4 MCP3208 has 8 ADC input (12 bits)
* $8 dsPIC30F 2011 microcontroller has 8 ADC inputs (12 bits). See [[dsPIC30F 5011 Development Board]] for details.
* $6 CY8C27443 Cypress PSoC microcontroller has 4 ADC inputs (14 bits) -- but what is the sampling rate? Also has 4 DAC outputs (9 bits).

* biosemi used analog devices AD7716 22 bit

The newest system is a dc amplifier without a high-pass, and all the low-pass filtering is digital

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OpenCircuits:Community portal

2007-06-24T08:42:23Z

163.192.3.146: /* MIDI electrical interface */

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

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== 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)

== 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)

== 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.

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== Requests For Help ==
Is there any way to ask for wise persons to write an article? I want to know about microphones for my Cannon Elura 100, (9V 3mm stereo jack? Where does the 9V come from?) and XLR mics and circuts. How can I make a mixer and a USB interface? Can we get an alert system to notify a requestor when the request is filled?

[[User:Negatron|Negatron]] 18:00, 20 February 2007 (PST)

: Yes, it's easy to start a rough draft of a new article.
: There are at least 2 "alert systems" built into MediaWiki.

: Alas, it takes time to convert that rough draft into a useful page of information.
: Near the bottom of page http://www.communitywiki.org/en/DavidCary , I whine about how difficult it is to force really smart people to talk about what *I* want them to talk about. :-/

: We are all volunteers here.
: Would you mind writing a little more about your "Cannon Elura 100"? Perhaps you could snap a "zoomed out" photo of the whole thing, and a "zoomed in" detail photo of its jacks and connectors. Then upload those photos?

: I'm a little confused at exactly what you want.
: Do you want a USB interface to your digital video camcorder?
: So you can ... what? plug in a USB mouse?
: If you make a rough draft of an outline of the article you want, with lots of "..." gaps to show the gaps in your knowledge you want to fill, it's a lot easier for people to fill in the "..." gaps.

: Do any of these XLR microphone circuits work for you?
* [http://www.epanorama.net/circuits/microphone_powering.html "Powering microphones" ] by Tomi Engdahl 2000
* [http://www.oldbird.org/mike_home.htm recording in-flight bird calls: "Microphone design and building instructions" ]
* [http://www.rcrowley.com/CamAdapt.htm "Microphone Adapters for consumer camcorders"]

: --[[User:DavidCary|DavidCary]] 11:01, 6 March 2007 (PST)

== 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

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Integrated Circuits

2007-06-24T02:35:23Z

163.192.3.146:

== Digital Potentiometers ==
[[Digital Potentiometers|Digital Potentiometers(AD5204)]]
The digital Potentiometers made by analog devices (AD5204) has 255 positions can be adjusted by the microcomputer that can receive commands from the computer. This is a great way for analog circuitry to have digital control. This is a chip with 4 digitally controlled POTs and the pots can be daisy chained to have multiple chips controled by a single SPI interface.

== Voltage Regulators ==
{|
! colspan="2" align="left"| Linear Regulators
|-
| align="center"|[[Image:Main-LT1528.jpg|69px|LT1528]] [[LT1528]]
| High current, Variable Voltage Regulator
|-
| align="center"|[[Image:TPS-V-Reg.jpg|69px|TPS V-Reg]] [[TPS V-Regs]]
| These are 3.3V and 5V LDO, Low-Noise Voltage Regulators. Very small SOT-23 SMD package. 150mA max current. Best used in battery applications.
|-
| align="center"|[[Image:Main-LM7805.jpg|69px]] [[Basic Voltage Regulators]]
| Variable voltage regulators, set output regulators, we give you the whole breakdown. Perfect for use with an external wall-wart power supply.
|-
| align="center"| [[Image:UA723CN_Symbol.gif]] [[The 723 Voltage Regulator]]
| Precision Voltage Regulator. Can be used as fixed or floating, variable, linear or switching.
'''NOTE:''' Only the DIP-14 version (image) has the Vz pin, which is used for negative regulators. The Metal Can and the Flat-Pack do not have enough pins so exclude the Vz.
|-
|