Check the actual voltage on the aref. If you're running only off USB, I have found that it could be off a significant amount if your usb voltage is low for whatever reason.
You can also use the .SetRange(0, 3300) on your pin method to get the millivolt conversion "for free". I'm guessing if your aref is actual at 3.26 or something you could do .SetRange(0,3260)...
Also check this thread on the LM35
I'd be curious to know about fluctuations in your readings, which I have been struggling with:
Analog Input Fluctuations
bill.french's Content
There have been 260 items by bill.french (Search limited from 03-July 23)
#4155 Analog voltage incorrect
Posted by
on 24 October 2010 - 12:04 AM
in
General Discussion
#3291 Can't connect via Visual Studio or MFDeploy, erase does not fix
Posted by
on 30 September 2010 - 05:25 PM
in
Netduino Plus 2 (and Netduino Plus 1)
Any progress recreating (and fixing) the original issue?
#5931 Netduino + SQL client (maybe System.Data.SqlClient)??
Posted by
on 09 December 2010 - 02:34 AM
in
Netduino Plus 2 (and Netduino Plus 1)
$query="insert into tablename values('.$url1', '".$url2"', '".$url3"');";
I can't help but mention the risk of sql injection attacks -- unless i'm misunderstanding how php works, this appears ripe for that sort of exploit. Not that there's much risk when messing around with a netduino, i think establishing good habits regarding injection attacks early on before bad habits take hold are really important.
Here's some info in regards to php:
http://stackoverflow...njection-in-php
... and my favorite sql injection attack:
#5877 Netduino + SQL client (maybe System.Data.SqlClient)??
Posted by
on 07 December 2010 - 08:23 PM
in
Netduino Plus 2 (and Netduino Plus 1)
I can't imagine sqlclient making it into the firmware...
You could easily log to sql using an asp.net app or a forms app, you could look here for maybe a starting point:
http://forums.netdui...ch__1#entry4637
#4756 MotorButton loop error? Update: Now more about Motor Driving.
Posted by
on 09 November 2010 - 07:12 PM
in
Visual Studio
Yeah, that diagram is the same basically as the right side of what I posted.
Vbe is the base to emmitter voltage.
Vce is the collector to emmiter voltage.
Ib is the current to base
Ic is the current through the collector
RC is the resistor to the collector <--i just edited this, i had it wrong!
Since you're just going to be using the transistor as a switch, you really don't need to worry so much about any of those to get started. They will be whatever they are. All you need to really worry about is RB and maybe the diode. Starting with an RB of 1k is a good starting point.
If you want to think of the transistor as something more than a switch (because they are so much more) in this case, think of the transistor as a current multiplier. Different transistors have different multiplication factors (the real name of which escapes me...) .. so, if you put in say 1ma into the base (Ib), that will allow say 100x (which is typical of common transistors at radioshack) the current to move from the collector to the emmiter (Ic). If you use a 1k resistor for RB, that gives you .0005 amps for Ib, which should multiply to .5 amps Ic, which should be enough to drive your motor.
Some transistors:
http://www.radioshac...oductId=2062586
Vbe is the base to emmitter voltage.
Vce is the collector to emmiter voltage.
Ib is the current to base
Ic is the current through the collector
RC is the resistor to the collector <--i just edited this, i had it wrong!
Since you're just going to be using the transistor as a switch, you really don't need to worry so much about any of those to get started. They will be whatever they are. All you need to really worry about is RB and maybe the diode. Starting with an RB of 1k is a good starting point.
If you want to think of the transistor as something more than a switch (because they are so much more) in this case, think of the transistor as a current multiplier. Different transistors have different multiplication factors (the real name of which escapes me...) .. so, if you put in say 1ma into the base (Ib), that will allow say 100x (which is typical of common transistors at radioshack) the current to move from the collector to the emmiter (Ic). If you use a 1k resistor for RB, that gives you .0005 amps for Ib, which should multiply to .5 amps Ic, which should be enough to drive your motor.
Some transistors:
http://www.radioshac...oductId=2062586
#4750 MotorButton loop error? Update: Now more about Motor Driving.
Posted by
on 09 November 2010 - 06:29 PM
in
Visual Studio
Here's what I would do. I am not an expert on anything so... you're on your own.
Looking at the below diagram, look at the circuit on the right, since a motor is an inductive load. I would skip RC, because I am hardcore. RB i would start with a 1k Ohm. I would use just about any NPN resistor, RadioShack should definitely have them, I think they sell a 10 count variety pack. For such a small motor almost any diode would do, something like this should be fine: http://www.radioshac...oductId=2036269
Is it safe to assume you understand the symbols in the diagram for the diode, transistor, etc?
Looking at the below diagram, look at the circuit on the right, since a motor is an inductive load. I would skip RC, because I am hardcore. RB i would start with a 1k Ohm. I would use just about any NPN resistor, RadioShack should definitely have them, I think they sell a 10 count variety pack. For such a small motor almost any diode would do, something like this should be fine: http://www.radioshac...oductId=2036269
Is it safe to assume you understand the symbols in the diagram for the diode, transistor, etc?
#4704 MotorButton loop error? Update: Now more about Motor Driving.
Posted by
on 09 November 2010 - 01:48 AM
in
Visual Studio
do you have or can you get at least a transistor and some resistors? I think you risk hurting your netduino hooking it up directly.
#4701 MotorButton loop error? Update: Now more about Motor Driving.
Posted by
on 09 November 2010 - 12:52 AM
in
Visual Studio
I'm pretty sure you're going to need at least a transistor and a diode to drive a motor -- i don't think the netduino (or most microcontrollers for that matter) can safely drive a motor.
#6831 Etched my first shield PCB...
Posted by
on 02 January 2011 - 03:30 PM
in
Project Showcase
I switched to the resist-etch positive exposure method.
Any links you've found useful? Sources on the boards you like?
#6829 Etched my first shield PCB...
Posted by
on 02 January 2011 - 02:00 PM
in
Project Showcase
I've done it several times, I've been surprised with how easy it is, actually, almost like magic. There's usually some issue with the traces, but a sharpie can correct it. If the toner transfer is too "rough" to correct, you can just clean it off and do it again. Acetone for cleaning never worked for me (maybe my wife's acetone is not actually acetone?), so I use Brakleen which should be available at walmart or any autoparts store.
PulsarProfix has lots of information, as well as some special paper i would love to try, as removing the paper seems to be the most problematic for me.
This site: http://www.riccibitti.com/pcb/pcb.htm probably is the closest to what I actually did.
PulsarProfix has lots of information, as well as some special paper i would love to try, as removing the paper seems to be the most problematic for me.
This site: http://www.riccibitti.com/pcb/pcb.htm probably is the closest to what I actually did.
#6821 Etched my first shield PCB...
Posted by
on 02 January 2011 - 05:52 AM
in
Project Showcase
Starting with Fritzing and using the toner transfer method, I've gotten my sous vide project a lot more physically solid on its own PCB. I've also added some headers for an LCD screen and buttons for the future.
In case it inspires someone to try etching their own boards, here are some pics:
1. Breadboard in Fritzing:
2. PCB in Fritzing:
3. PCB with toner, pre-etching, with some sharpie touch-ups (this is actually an older layout, but I forgot to take pics of the new layout)
4. Etched and tinned:
5. IC Side of the board:
In case it inspires someone to try etching their own boards, here are some pics:
1. Breadboard in Fritzing:
2. PCB in Fritzing:
3. PCB with toner, pre-etching, with some sharpie touch-ups (this is actually an older layout, but I forgot to take pics of the new layout)
4. Etched and tinned:
5. IC Side of the board:
#4764 Analog Input help...
Posted by
on 09 November 2010 - 08:09 PM
in
General Discussion
I'm sorry, I don't know, then. I added some to my shopping cart at sparkfun, if I get enough other stuff to make an order I'll try and get one hooked up to see how it works. I also updated my drawing to show a line from 3.3v to aref, but I don't think that has anything to do with it.
#4778 Analog Input help...
Posted by
on 10 November 2010 - 12:37 AM
in
General Discussion
Are you talking about the http://fritzing.org/ diagrams? Fritzing is awesome.
#4760 Analog Input help...
Posted by
on 09 November 2010 - 07:31 PM
in
General Discussion
ok i think I got this right -- i believe the right most pin is the - and the center pin is the +:
Is that about what you're doing, with the multimeter/analog input hooked up after the resistor?
Is that about what you're doing, with the multimeter/analog input hooked up after the resistor?
#4746 Analog Input help...
Posted by
on 09 November 2010 - 06:04 PM
in
General Discussion
The analog input only supports 3.3v -- but if I'm reading this right, a reading of 4.88v equates to 488K, which is 419F, which is 215C ... so unless your house is on fire, something else is wrong.
#4688 Analog Input help...
Posted by
on 08 November 2010 - 11:39 PM
in
General Discussion
I don't think it works that way, but I really don't know. Why do you have the analog input tied to the adj pin?
#4685 Analog Input help...
Posted by
on 08 November 2010 - 11:19 PM
in
General Discussion
Oz: Are you sure that diagram is right? It doesn't quite make sense to me. Maybe talk me through it? Why isn't aref tied to the 3.3v line?
#4679 Analog Input help...
Posted by
on 08 November 2010 - 10:14 PM
in
General Discussion
The analog input pins basically work by returning a value between 0-1023 based on the voltage that is on the pin, relative to aref. Aref is the "analog reference" and sets the "ceiling". Typically you'd tie aref to 3.3v - which is it's maximum. Then, if you put 3.3v on the analog pin, you would get a reading of 1023. If you tied the analog input to ground, you'd get a reading of 0v. if you put 1.6v on the analog input, you'd get a reading around 512, or half the range. The analog inputs can handle a max of 3.3v.
Here's a link to some sample code:
analog sample code
In that code, there's a line:
This is the default, so it effectively doesn't do anything at all; but, if you do:
...your readings will match roughly with the actual voltage in millivolts. So, if you put 1.6v on the input, you'll get a reading around 1600 instead of 512.
Hopefully this makes sense?
Here's a link to some sample code:
analog sample code
In that code, there's a line:
AP0.SetRange(0, 1023);
This is the default, so it effectively doesn't do anything at all; but, if you do:
AP0.SetRange(0, 3300);
...your readings will match roughly with the actual voltage in millivolts. So, if you put 1.6v on the input, you'll get a reading around 1600 instead of 512.
Hopefully this makes sense?
#4762 Analog Input help...
Posted by
on 09 November 2010 - 07:56 PM
in
General Discussion
and you're not using the far left (adj) pin at all, right?
#4749 Analog Input help...
Posted by
on 09 November 2010 - 06:15 PM
in
General Discussion
I'm sorry, I don't know. According to this picture:
If your room is 72 degrees F, which is 295 degrees K, you should have a reading of about 2.95V, I think.
When you're measuring with the multimeter, is the netduino involved in the circuit at all? I would start with the netduino out of the picture entirely a focus on getting the right readings on a multimeter, then focus on getting them well below 3.3V to be safe for the analog inputs.
If your room is 72 degrees F, which is 295 degrees K, you should have a reading of about 2.95V, I think.
When you're measuring with the multimeter, is the netduino involved in the circuit at all? I would start with the netduino out of the picture entirely a focus on getting the right readings on a multimeter, then focus on getting them well below 3.3V to be safe for the analog inputs.
#4753 Analog Input help...
Posted by
on 09 November 2010 - 06:32 PM
in
General Discussion
Yeah, I don't know then -- using the 5v should be fine. Can you post a picture or a diagram or something? I wish I had one of those sensors to try it out myself.
#5504 What's the status of Onewire?
Posted by
on 29 November 2010 - 11:23 PM
in
Netduino 2 (and Netduino 1)
Hello! I ordered some DS18B20 temperature sensors, before I realized I had no idea how to interface them with the netduino -- what's the status of onewire? What do i need to do to support onewire and interface with the DS18B20?
Thanks!
#5615 What's the status of Onewire?
Posted by
on 02 December 2010 - 01:48 AM
in
Netduino 2 (and Netduino 1)
Thank you, that is very good information, and I understand you perfectly.
I ordered one of these: http://www.phanderso...mp/onewire.html
It seems similar to your suggestions. I will let you know how it goes!
#6080 What's the status of Onewire?
Posted by
on 14 December 2010 - 01:02 PM
in
Netduino 2 (and Netduino 1)
It is difficult/impossible to get the precise timing needed for onewire running in managed c# code.
Someone wrote a low level onewire driver, but it's not integrated into the netduino firmware yet, and since I'm not ready to compile my own firmware, I needed another solution.
Some might look at this as some sort of disadvantage of the netduino, but I think it illustrates the power of the device, since I have been able to create and debug my "business logic" and "network logic" very easily in c# on the netduino, with the precise timing stuff offloaded to dedicated devices. This is a paradigm that works well for me.
#5664 What's the status of Onewire?
Posted by
on 02 December 2010 - 08:18 PM
in
Netduino 2 (and Netduino 1)
My chips should come today, my sensor is due tomorrow, so i should have some news soon.
I bet if you email him directly and ask him to just mail them, it should be much cheaper... otherwise, I can mail you one of mine once I get it going.
