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Recent Posts

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81
General Discussion / O'Plaza remote relay question
« Last post by JS on June 06, 2016, 04:50:00 AM »
Hi there,

Thanks for the O'Plaza info here and on instructables.com.  Can you provide a simpler schematic or explain how to connect it to a light bulb? I'm a novice trying to do something very simple, go into the pos/neg from a 12v battery pack and out to the pos/neg on a lightbulb.  I've tried various combinations of two wires coming out from the 3 connectors and I hear the clicks but the bulb's not coming on. In the meantime continuing to scour the internet but it seems everyone's using this product for more complicated projects. Thanks.
82
General Discussion / Schmidt trigger?
« Last post by BigMan52 on May 30, 2016, 17:14:45 PM »
Hi,

I am working on the attached project and wondered if someone would mind checking my work. I have an electrical installation background and not much experience in electronics.

a. I have worked this out as +/-1.5V using +/-3V as the saturation voltage.
b. I have drawn an inverted output waveform with flat peaks at +/-3V (not shown here)
c. Struggling a bit with this. I am assuming it is an inverting comparator op amp and is very much like a schmidt trigger. The comment I make about the results is that the calculated threshold values are assumed to be constant and they are not in reality.

I look forward to any feedback.
83
Analog discussion / LDR
« Last post by Bahad628 on May 20, 2016, 15:58:11 PM »
Hi to all

I need help to make a dimmer with ldr that is analog.
the input voltage is 12v.
please have a look at picture how shall I do for the 4x7seg led dim acording to
light of ldr, in day time full and night time dim the led's.

any one that kan help me with suggestions of this.

the led display is common anod
Thanks in advance
84
General Discussion / circut board blueprints
« Last post by inivode on May 06, 2016, 05:34:55 AM »
L325.00 (MOD: PRG101LS1) I'm looking for circus board schematics but cannot find any...
85
General Discussion / Thermocouples
« Last post by mcm200 on April 24, 2016, 22:38:43 PM »
Hello there! I have a question that has been haunting me for long. Recently I read over and over the thermocouple article on pcbheaven and the question arose again. Let?s see for example this situation (depicted in the TC article when cold compensation is explained): we have the TC wires attached to a pair of copper wires on the connecting isothermal block. I cannot understand why, despite of both junctions on the block being of different nature, let?s say chromel-copper and alumel-copper, this doesn?t create a source of error when both these junctions are at the same temperature  (say 0 deg C). I do understand why two junctions of  equal  nature give zero output when held at the same temperature, but not in the case of different junctions. Can anybody help me with this? Thank you !
86
Your projects / Re: Water management system
« Last post by cheerio on April 01, 2016, 01:26:04 AM »
Did work on this for a while longer. and right now i am rebuilding all of it because it looks like shit ;)
i want it to be tight and nice. will put something more up here soon
87
Your projects / Re: Prometheus - A Desktop Machine that Makes Circuit Boards
« Last post by Spork Schivago on March 28, 2016, 22:07:01 PM »
Hello.   Can this device be used to make stencils as well?   Either out of transparency sheets or thin sheets of stainless steel or something?

Also, how much do you think it would cost to make over all?   For the whole device?  Thanks and best of luck!!!   Keep us posted on your progress please!
88
Your projects / Re: Prometheus - A Desktop Machine that Makes Circuit Boards
« Last post by facembani223 on March 15, 2016, 23:34:56 PM »
this is super cool, hope you will get funded on Kickstarter.
I am working on my own project based on Raspberry Pie and Arduino Controllers, hope i wll get at your level :)
89
General Discussion / 555 Breathing (Pulsing) LED
« Last post by ronwireland on February 14, 2016, 14:13:11 PM »
Hello

I am new to this forum and new to electronics.

I am currently trying to build the 555 Breathing (Pulsing) LED and the most I can get is the LED comes on and then goes off and that is it.. I see looking at the photo of the breadboard there are 2 resistors that seem to nowhere, 1 off pin3 and 2 toward the bottom right corner? The only other change on mine is the 2N2222, I am using a 2N2222A. Also have slightly different potentiometer but they are 10K. Can someone please help?

Ron
90
Your projects / Re: Measuring PC fan TACH problem - fan slows down
« Last post by kam on February 05, 2016, 10:05:05 AM »
the GPIO draws current in the scale of uA. So it should definitely have no effect on the fan's operation. Use a miliammeter to see if indeed the chip draws a few uAmps of current when connected. If not, then most likely the input is broken.
Other than that, i can only think that the fan's internal circuit is as bad as hell. You can use an op-amps to interface the output. But still the uC draws only a leakage current when the pin is an input.
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