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1
General discussion (digital) / Re: clock circuit problem
« Last post by kam on May 20, 2013, 18:21:05 pm »
the filtering capacitors are used to smooth the input voltage and remove spikes and EMI/RFI. You need to use base resistors for the transistors! Check the transistor specifications for the one you use.

As for the ULN, most likely you've fried it big time.
2
General discussion (digital) / Re: clock circuit problem
« Last post by lefteris_ on May 19, 2013, 22:06:15 pm »
I'm sorry,i forgot to mension that the 4 transistors are not 2n222 but c828...  :-[ :-[ :-[

does the filtering has to do with the clock rate(faster than convetional time)?or it is just the parasitic capacitance?

why the pic does not outputs stable signals for each segment?there must be alot of noise.

I will do the filtering capacitors.

Another thing which i say WTF is going on here is that when i connect the signal for the A segment to the pin 1 of the uln and the led's - to pin 16, the led stip turns on with the pin 8, which is the emitter, unconnected...  ???WTF? I think that the circuit got crazy after so many tests...... :o :o
3
General discussion (digital) / Re: calibrating a sensor
« Last post by cheerio on May 19, 2013, 19:46:01 pm »
yes
4
General discussion (digital) / Re: calibrating a sensor
« Last post by kam on May 19, 2013, 17:40:15 pm »
Are you trying to re-create the temperature to voltage characteristic???
5
General discussion (digital) / Re: clock circuit problem
« Last post by kam on May 19, 2013, 17:36:03 pm »
You use 4 2n222 transistors with no resistor base... I wonder how they operate! And i wonder how the PIC is not fried!
So, 2n2222 typical have 40hfe (if i can recall correct), you need say 8x20ma for each digits, say 200mA (always oversize), so the base current must be at least 5mA, PIC voltage is 5v... so use base resistors of 1K for each 2n2222

Next, you need filtering capacitors, one 100uF before the 7805 and one 1uF after. Then you need one 0.1uF as close as possible to the PIC's supply.

The ICL is a nice touch!

I think it will then work.
6
General discussion (digital) / calibrating a sensor
« Last post by cheerio on May 19, 2013, 12:44:20 pm »
Not sure if this is really digitial or more analog diskussion.
Well i want to know how you calibrate a sensor. to be more precise i speak about a sensor that has an analog output that is converted by an ADC unit inside a MCU.
I always look for a linear offset first. After i have compensated that i do the following:
i write down the corresponding ADC value for a given sensor value. for ex. i write down ADC 50 for 10°C. then i increase th sensor value using a stepping that makes sense for the application. for ex. if i want to measure 0-500°C i would measure the ADC Value for each 10°C increase.
after that i have smth like this:
50, 10
55, 20
65, 30
75, 40
80, 50
...

what i do now is that i look for simmilar ADC increases per °C:

50, 10-> X
55, 20-> .5
65, 30-> 1
75, 40-> 1
80, 50-> .5
...

next step is to do a very nasty if else chain where i check if the ADC value is for ex. between 55 and 75 then i do the calc like this:
°C = 55+(ADC-20)*factor
where factor is 1 in this case


this works very accurate but it is very nasty to do and you always need a good reference sensor to do this.

How do you calibrate your sensors? do you have better ideas to compensate not linear errors?
7
General discussion (digital) / Re: clock circuit problem
« Last post by lefteris_ on May 18, 2013, 20:46:54 pm »
This is the scematic

I read on the net that i have to use pull down resistors in order to control effectively the led strips with the uln!
8
Your design ideas / Re: Air conditioner control
« Last post by kam on May 18, 2013, 12:59:13 pm »
Lets invert them

Code: [Select]
0000 at 17
0001 at 18
0011 at 19
0010 at 20
0110 at 21
0111 at 22
0101 at 23
0100 at 24
1100 at 25
1101 at 26
1001 at 27
1000 at 28
1010 at 29
1011 at 30
and convert them to dec:
Code: [Select]
0 at 17
1 at 18
3 at 19
2 at 20
6 at 21
7 at 22
5 at 23
4 at 24
12 at 25
13 at 26
9 at 27
8 at 28
10 at 29
11 at 30
it really makes no sense... You can just use this pattern as-is... copy it and use it. But it is really crazy.
9
Your design ideas / Re: Air conditioner control
« Last post by fuzail on May 17, 2013, 17:58:23 pm »
yeah looking at your project on the fidiji airconditioner helped me alot.
what i don't understand is how do you select which of the on-off sequence is a 1 bit and which one is a 0 bit.
through some trial and error and lil bit of luck i was able to decode how the bits were set on one ac.

the next ac i am totally stumped.!
the way the bits change is so random (at least to me, i am poor when it comes to these binary/boolean logic)

Code: [Select]
1111 at 17
1110 at 18
1100 at 19
1101 at 20
1001 at 21
1000 at 22
1010 at 23
1011 at 24
0011 at 25
0010 at 26
0110 at 27
0111 at 28
0101 at 29
0100 at 30
those bits could however be inverted. as i interpreted it in the wrong way i.e 1 instead of 0 and 0 instead of 1.
10
General discussion (digital) / Re: clock circuit problem
« Last post by kam on May 16, 2013, 11:02:07 am »
oh, and please upload schematics with images, the eagle files you uploaded do not work for me
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