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1231  Using Arduino / Microcontrollers / Re: programming attiny 85 error on: January 07, 2013, 01:44:51 pm
Pins 7, 8, and 9 output the status of ArduinoISP; use a ~500R resistor and an LED and they will flash based on the ISP status. Pin 9 is the heartbeat LED and will pulsate so you know ArduinoISP is running; that will verify that your caps are working to disable the reset.
1232  Community / Local Groups / Re: NE Iowa/SE MN/Westren WI or Des Monies IA? on: January 06, 2013, 11:04:40 pm

Liudr, what do the AX-man stores stock? Just a lot of electronic stuff?
1233  Community / Bar Sport / Re: I bought a battery on: January 06, 2013, 10:48:07 pm
Roughly you charge lead acid batteries at a rate no more than 1/10th their capacity for optimum lifetime. So your 30Ah battery would be charged at 3A. But the charge rate is not as important as avoiding discharging or 50% or leaving it sit off a charger for months at a time.

It's also worth noting that a sealed battery is charged to a different float voltage than a flooded (car) battery. Your charger offers no ability to choose the battery type; a slightly more expensive charger would.

Good reading for a similarly sized AGM battery showing how discharge level/rate affects battery life.
1234  Using Arduino / Sensors / Re: Sensing the impact of a projectile on: January 06, 2013, 09:42:39 pm
My main worry is to limit the signal going to the arduino.
With the microswitch it is easy: look for at break in the circuit.
But with the piezo, I'm afraid that I'll fry the pin with the generated voltage.

1235  Using Arduino / Sensors / Re: Generating signal for TSOP34836 IR receiver on: January 06, 2013, 09:34:21 pm
LED showing that signal is received, blinks for very short periods, etc. I can't understand is it some problem with my code (maybe I generate not exactly 36kHz...?) or TSOP34836 is just not intended to receive such signal?

You're right -- they won't like the signal. See page 5 of your datasheet. There needs to be pauses between bursts of blinks or the receiver will reject it as noise.

The only IR receivers I'm aware of that will accept a continuous signal are the Vishay TSSP4038 and TSSP58038.
1236  Using Arduino / Microcontrollers / Re: Loading bootloader for AT328P on: January 06, 2013, 04:27:00 am
That's not an ISP header you're connected to. The pins are unpopulated in the middle of the board, right underneath where it says "AT328 ISP".
1237  Using Arduino / Project Guidance / Re: Hardware architecture for UDP in WIFI on: January 06, 2013, 04:02:14 am
The driver for the wifi interface shouldn't be involved in layer 4... why would implementation of UDP be any different for this board versus any other ethernet adapter?

Because the ATMega chips have a pittance of memory and clock cycles. They need help.
1238  Using Arduino / Sensors / Re: Reading Strain Guages / Scales on: January 04, 2013, 09:09:09 pm
Firstly I am getting readings that fluctuate somewhat. The analogue read value changes by 1-2 in what appears to be a oscillating pattern. (period of about 1.5seconds). Any thoughts or do I just need to live with it? The change appears to be happening in the INA125. Tying the analogue input to other voltage sources, such as the ref voltages on the INA125 gives stable results. Any suggestions for filtering, or changes to the circuit?

The datasheet for the ATMega chips will state a 10 bit precision, +/- 2 LSB accuracy. In other words the most you can rely on is 8 bit accuracy.

It seems that the appropriate route would be to add an additional ADC converter to get more bits of accuracy. I'm no expert though and also still experimenting myself.

Secondly, I am not able to obtain results that agree with real world weights. I have made the changes to the code required for the reference values and tried several different values. I have also tried a smoothing using code based on the Smoothing example in the IDE. But what I am finding is the output isn't linear. So the map function results to values that don't agree with the real weights of objects. It appears better at the lower end with the heavy weight skewing the results.

I don't think load cells are expected to give a linear curve for weight vs voltage. The thing to do would be to sample readings with different weights (0Kg, 10Kg, 20Kg, etc.), plot those using a spreadsheet, and then use that spreadsheet's facilities to find the curve of best fit. The resulting formula will give your voltage to weight conversion.

Third problem, any advice on getting the output of the INA125 to run near 0volts for no load on the scale and nearer to 5 or 3.3 at full load. (100Kg).

The solution is to balance the bridge using a resistor (resistors) between the excitation and output lines. I'm not sure that's a good idea though as any resistors you add to the bridge will introduce new problems with the difference in sensitivity to temperature of the load cell's resistors and your resistor. Best bet is to grin and bear it?
1239  Community / Bar Sport / Re: Your latest purchase on: January 03, 2013, 09:00:48 pm
The BT master/slave units were less than $8, I have seen BT units on eBay and DX for less than $7 but I dunno the differences since LC sells BT master and BT slave as well as the dual-units and I can't read Chinese to know what-all the differences are so I ordered the best they make.

They are programmable from slave to master / etc, or it might be dependent on the firmware as to whether it can be switched. It's the same hardware, at any rate. I recall stumbling across a firmware download for these modules so ... something to look for perhaps.

Stuff to read if you're bored:
1240  Using Arduino / Project Guidance / Re: Wind turbine charge controller prototype/shield on: January 03, 2013, 08:41:09 pm
If you put a blocking diode in there, you are dead. In my opinion, forget the blocking diodes, just have your controller turn the panels off at night.  Relays suck power for their coils, but only 1-2 watts for 60-120 amps of current capability. That is a lot less than losses in 60 amps of blocking diode. (like 20-30 watts)

Take another look at Tim Nolan's project to see how he uses mosfets for the blocking. More generally, he really does a great job of explaining his circuit and the various sections of it.

I agree with you on dropping the buck/boost for simplicity. Assuming the panel/turbine and batteries are matched well the batteries won't care too much if you overvolt them a little so long as you keep the current within bounds (or is that saying the same thing?). An enduser can always pop on an external module for buck/boost anyway.
1241  Using Arduino / Project Guidance / Re: First Project with the Arduino - Sous Vide - Dimmer / Heater on: January 03, 2013, 03:58:48 pm
If you know the volume of your cooker then you can calculate pretty closely how much power you need to get it up to temp. It comes out to about 2.42W to raise 1 gallon of water 1 degree F in 1 hour. Your tank will cool off of course but bringing it up to temp is where you'll use the most power.

What if I changed my power to a percent and then took 10 secs and divided it by that percentage. So if it was 50% I would leave the heater on for 5 secs and off for 5 secs? 70% would be on 7 secs off 3 secs.

Only someone from Clinton would do something like that smiley-wink. If you have any temperature reading of the water then the PID library is pretty straightforward to use to help you control the heater on/off. A DS18B20 probe in a stainless steel housing (~$10) is commonly used for water temperature sensing.
1242  Using Arduino / General Electronics / Re: Schematic review/questions: IO board of doom on: January 03, 2013, 11:35:29 am
The two 595s at the top of the schematic appear to have their SCK/SCL lines crossed.
1243  Using Arduino / Sensors / Re: Temperature sensor in up to 800 C degrees aplication on: January 03, 2013, 03:32:43 am
With no cold junction compensation you should not get more than ~10C error according to that AD-369 datasheet, but that is including ambient temperatures well outside of human comfort.

NIST publishes tables/formulas for calculating temperature from thermocouples if you use a plain A/D converter. An MCP3424 would give you four channels for ~$4 and you can have up to nine on an I2C bus. But it's a SOIC and the 18bit conversion rate is a bit slow (3/second).
1244  Using Arduino / Sensors / Re: IR detector under direct sunlight on: January 03, 2013, 02:50:55 am
Find a laser module with a focusing element and "unfocus" it. You can get a pretty large spot.
1245  Topics / Robotics / Re: How to prevent gripper holding too tight? on: January 02, 2013, 12:52:23 am
Maybe your chickens have an iron deficiency.

Any current sensing circuit to the gripper's motor will give you an indication of how much force is being applied. It will still work with an RC servo as well. Murphyslaww, perhaps you were thinking of the code that would tell you the servo's position based on how much current was being used by the servo (a moving or pushing servo uses more power than a stationary one).
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