46
General discussion / Undervoltage detector patent application
http://www.faqs.org/patents/imgfull/20110025518_01
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Topics
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Topics - matseng
http://www.faqs.org/patents/imgfull/20110025518_01
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47
Project logs / PAW9 - MrRef
This week I'm in Bangkok for some business meetings, but it won't stop me from doing this weeks PAW.
Since the last PAW was about as simple as it can be, just a small pcb with a bunch of holes drilled into it, I'll plan to do something a little bit more fancy for the PAW.
Unless you have a properly calibrated "serious" DMM like the Agilent 34410A or the 8.5 digit Agilent 3458A or even a Fluke 87V you really can't be sure that your $20-$50 DMM is displaying values that are not too far from the real value.
So a high precision voltage (and possibly also a semi-high precision current) generator might come in handy to check the accuracy of your DMMs.
The MAX6350-series are high precision voltage references (max 0.02% error) and a typical tempco 0.5ppm/°C (=0.00005%) so it basically won't be affected by temperature variations at all.
The 0.02% error might sound very good, but it's actually 1 mV for a 5 volt reference, so the output could theoretically be 5.001 volts. This is good enough to calibrate a standard 3.5 digit DMM, but it might be nice to have something more. Luckliy the output can be adjusted for higher precision if needed, something that of course woule require a properly calibrated 6.5 or 8.5 digit meter to do...
If I would to sell a few of these boards (pre-built) I'm thinking of having my 6.5 digit Agilent re-calibrated and certified so those MrRefs could be calibrated for an order of magnitude higher precision than the initial 1 mV.
The MAX6350 is available in 2.500, 4.096 and 5.000 volt versions and I'm leaning towards the 5 volt version and then possibly either include a selected high precision resistor to add a 1mA output on the board as well or including a voltage divider to add a 1 volt output.
The chip needs at least 8 volts to do its job properly so I plan to run it from four lithium button cells in series.
I think that the 1mA current output would come in more handy than a 1 volt output - what do you think?
The output terminals would of course be gold plated 4mm banana jacks, but I'm debating with myself if I have to put them at the "standard" 3/4 inch distance or not. It would be much easier to make a small pcb without this constraint. Any thoughts?
48
General discussion / One more PCB fab house - Cheap stencils
Same specs as Seeed/Itead: 6/6 mil T/T, 12 mil vias, 32 mil text
Standard 95% E-test (Seeed 50%)
10 pcs 5x5cm HASL Green = $10 (Seeed $10)
50 pcs 5x5cm HASL Red = $40 (Seeed $55)
100 pcs 10x10cm HASL Green = $127 (Seeed $190)
100 pcs 10x10cm ENIG(gold) Black = $151 (Seeed $249)
Aaaaaaannnnnnddddd....! Wait for it! A Solder paste stencil as an add-on to the order = $24
(No mention if it's just a kapton stencil or a lasered/chem etched stainless steel stencil.)
49
General discussion / Safe electrical installations - or maybe not
Four out of the five fluorescent lights mounted under the cupboards above my sink and kitchen worktops doesn't work, and moving the working tube to the non-functioning holders shows that it's the electronics in the holder that's broken. So I removed one of them and discovered that they are only connected with two wires (230 volts) and no protective ground. (Not so good especially when mounted over the sink).
The electronics package is mounted in a squareish aluminum tube and the pcb is half wrapped in some insulating sheet. But the tops of the high voltage caps are fully exposed and can easily touch the very squishy and bendable aluminium tube.
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And have a look at the bottom of the pcb. Remember that 230 volts are connected to those wires and the isolation distance on the pcb is like 0.3 mm or so. Not the 2.5 or 5 mm as mandated in many specs. And the soldering.... There are loose wires sticking out from the cables and touching the other tracks.
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I think I'll rip this shit out and install some 12 volt LED lightning from Ikea instead...
50
Project logs / PAW8 - NU-FitHole
This weeks PAW will be extremely simple - it's not even a breakout board, but it might still come in handy for people making PCBs. The FitHole is a tool for testing what drill size that best fits a part that you're making a library footprint for.
It have holes in sizes from 0.4 mm to 2.3 mm in increments of 0.1 mm, plus a hole that is 3.0 mm as well as a 6.35mm that is Seeedstudios largest standard drill size.
The 6.35-hole might also be used to put the tester on your keychain so you don't lose it. :-)
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51
General discussion / Some soldering before bedtime....
The pitch of the 12 connectors is 0.65mm so it was easy to solder wires directly to the flex connector and connect it up to a 0.1" pin header.
Testing it will have to wait until tomorrow evening....
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52
General discussion / Nice & cheap finds at eBay
I invite others to list their finds here as well... Please add a picture and either a direct link to the item - or even better the the url used to find it.
53
Project logs / PAW7 - Mainslog_Sensor
Last week I did the PAW6 Game Of Life -board (viewtopic.php?f=56&t=5034) plus an extra PAW X1 breakout/utility board (viewtopic.php?f=56&t=5053) since Seeedstudio gave out vouchers for a free PCB order during the weekend.
This week I'll just finalize and order a board that I started on earlier. It's the sensor board for the mains (wall power) logger that will collect statistics about voltages and exact frequencies over a period of time.
The project will be split up to two pcb's. The first board is this PAW - the sensor board that makes the actual measurements and sends the data to the second board. The second board that I'll do in a later PAW will handle the storing, calculation and display of the received data.
The sensor unit will be built on a SoB DP5050 boards and will be powered by the mains using a transformerless power supply. Since this means that the entire board will have dangerous voltages on it so the data will be sent over an optocoupler so the second board will be isolated and safe from the mains power.
The schematic is rather simple:
To the left is the capacitive-style transformerless powersupply that is able to deliver up to about 30 mA.
D5,R2,R3,R8 is a half wave rectifier and voltage divider to scale down the 230 volt RMS to a voltage that the microcontroller can read with its ADC1 -input.
R4 and R7 is limiting the current into the frequency sense input pin. The internal clamping diodes in the microcontroller can safely clamp 230 volts to 5 volts as long as the current is below 1 mA.
And to the right the optocoupler is connected in series with an indicator led that will flash at each data transmission.
The firmware will measure the peak voltage during 50 or 60 cycles and then transmit the value over the optocoupler to the logging board. Since there are no variable timings or evil operating system that will disturb the timing the second board can use the beginning of each transmission as a 1-PPS (One Pulse Per Second) to accurately measure the mains frequency - the second board must have a very stable reference clock to do this, but that is another problem for another day.
54
General discussion / Need project ideas for reflective IR sensors
But what should I do with them? They seem to have a range of max 5-10 cm under good conditions which limits the types of projects. A theremin is out of the question.
And I would like to avoid doing a cofee table full of leds that lights up as you sweep your hand over it. That has been done too many times and I've already done too many led'ish projects lately.
Touchless bongo drums with analogue dampened oscillators to get that cheesy 70'ies sound?
Anything else? Some kind of game?
55
Project logs / PAW X1 - SuperCombo1
Since Seeedstudio have a campaign this weekend where every PCB order gives a free $10 PCB voucher I feel that I have to throw in an extra project today . So here it is.... The SuperCombo1 extra PAW X1!
This is a combo breakout and utility board with five different designs. Two of the designs, the Single Wire LCD backpacks, I did PCBs for a couple of month back, but they were flawed and needed a few greenwires to work properly. This version should hopefully work better. viewtopic.php?f=56&t=4484
The third design is a thru-hole version of PAW1 NU-Xtal. viewtopic.php?f=56&t=4891
The fourth design is a USB breakout board with a Mini USB on one side and a Micro USB on the other.
The fifth design is a small switch mode PSU targeted for OLEDs and programming voltage for microcontrollers. It's based on the FAN5331 chip.
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56
General discussion / Seeedstudio order tracking
Quote
01/07/2013 Confirmed
01/07/2013 Confirmed PayPal status: Completed @ 02:19:40 Jan 07, 2013 PST Trans ID:2X688196Y7312318 Amount: 41.61 USD
01/07/2013 PCB Confirmed This order has PCB item(s)
01/08/2013 PCB Processing PCB File:D67933_RetroTime.zip is now in file checking process.
01/08/2013 Pending Hole connection is 3mm, at least to 6mm can be available. PCB file name: D67933_RetroTime.zip
01/10/2013 Pending Outside a small circle inside the large circle intermediate connection too narrow to be produced.
01/10/2013 PCB Confirmed New PCB file uploaded
01/10/2013 PCB Processing PCB File:D67933_RetroTime_v2.zip is now in file checking process.
01/10/2013 In production D67933_RetroTime_v2 is starting producing.
01/13/2013 In production D67933_RetroTime_v2 is ending producing.
01/14/2013 In production D67933_RetroTime_v2 is coming back from production workshop.
57
Project logs / PAW6 - GolGrid - Conways Game Of Life
Last weeks board was a simple breakout board so this week I'm planning to do something a little bit more elaborate. I've been playing with programs emulation Conways Game Of Life (http://en.wikipedia.org/wiki/Conway's_Game_of_Life) since the early 80'ies on computers. But now is the time to make a hardware implementation of it.
A GameOfLife in hardware is certainly not a new or unique idea, Adafruit is selling a kit (by Dropout Design) for $17 with 4x4 pixels that can be linked into larger arrays with more pixels.
This weeks PAW will be a similar board, but SMD and using a small and cheap 14 pin PIC as the board microcontrollers. Unlike the Dropout board that have an elaborate communication between the boards to determine the next state of the grid my boards will merely be slave boards that only displays what the master tells them to display on the leds.
So one of the boards in the array of boards will have a more powerful PIC on it that will act as the master and send the grid updates to all slave controllers. The master board will probably also have a USB port for both power and maybe to upload data from a PC to be displayed on the GolGrid array.
Each 5x5 cm board will have 16 leds in a grid of 15mm. This means that if the boards are separated by exactly 10 mm the spacing between the outer leds of adjacent boards also will be 15 mm - making up a nice even grid of leds.
To easily get the distances between the boards correct I'll use standard paper staples since they are 13 mm wide (crown width) so if I put vias 1.5 mm from the edge of the board I can just plunk down a staple and get the 13-1.5-1.5=10 mm distance and at the same time transfer power and data between the boards.
Three staples in each direction is enough for VCC, GND and a common databus. Having a common databus means that each board needs to have a board number or board coordinate stored in its eeprom so it can filter out just the messages that are meant for it.
I'll probably use a PIC16F1824 which cost just over a dollar. Add $0.60 for leds, $0.30 for resistors and $1 for the pcb and the parts cost for a board in small quantities is only about $3 to $3.50.
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General discussion / I'm sad today :-) My Bus Pirate doesn't have holes..
Quote
Order Date: Wednesday 07 October, 2009
Order Information - Order #4441
Qty. Products Total
1 ea. [Preorder] Bus Pirate v3 (assembled) $27.15
59
General discussion / Battery clips short-circuiting battery
I got some battery clips to make a 23A battery (a tiny 12 volt battery) -holder for an upcoming project. But when I snapped in the battery in the holders it was short-circuited thru the battery casing by the clips. That seems a more than a little bit unusable to me. How the heck are you supposed to use these clips?!?
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Project logs / PAW5 - Oledy, a generic OLED breakout board
This week I'll be busy with other things so I'll make this weeks project very simple. In fact tt's so simple that I've already did it last week. :-) So unless someone comes up with any ideas for changes I have this "week off".
The Oledy board is a 5x5 cm board meant to be cut in half ending up with two boards 2.5 x 5 cm. Each board have a two 16-pin headers that are connected to four arrays of 32 solder pads. All eight pad arrays are of different pitch to match different OLED displays.
The piches are 0.50, 0.60, 0.62, 0.65, 0.70, 0.80, 0.845 and 1.00 mm
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