Solarizing a picaxe

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noise0

Member
santacruzbob said:
lol.. for low voltage zeners the holding current is normally 20mA or higher
good luck, Bob
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thanks bob for the tip about zener, in the future i will try to remember i have to give at least 20mA to obtain proper functionality

anyway , in this project, i do not care about zener specs, the only important think is to obtain "consistent" readings
everytime the voltage exceed the threshold the ADC reading exceed a certain value...
that's all i need
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N

noise0

Member
what is the maximum value of a pulldown resistor in order to avoid input commutation?
With 100k it semms ok.. can i use Mega ohm ?

posted last revision:
note i am planning to make it a bit more modular
eyes, feelers and leds will not be soldered to the critter but wil become detachable modules by 2.5mm SIL strips

the size of the body of the critter will be 66 x 37 mm (the size of the solar cell)

there will be 3 overlapper floor of the same size (sandwitch robot style)
1) the solar cell
2) picaxe + 74240
3) caps + motors

the two input plug will be put on the front side of floor 2 and 3
output plug in the back side of floor 3
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hippy

hippy

Technical Support
Staff member
With 100k it semms ok.. can i use Mega ohm ?

That might best be a case of try it and see or perform some testing with various resistors using a PICAXE on a stable PSU. Once you've found an apparent upper limit, start adjusting PICAXE parameters, voltage, temperature etc and see how it fares then.

In my limited experience, once you get towards mega-ohms things start to get a bit shaky, with only micro-amps of current involved. At 'some point' a pull-down doesn't seem to have any more effect than leaving an input floating.
 
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Mycroft2152

Senior Member
When I solarized an 08M a few years ago, I used a Green LED and a 100K resistor, instead of the Zener. Though one of the 2.56 volt reference chips is the best choice.

For the uber technical people, yes the LED reference voltage will vary slightly. But for this purpose it is not significant.

Myc
 
M

Mycroft2152

Senior Member
N,

You can save one pin by making the LDRs into a voltage divider. This takes advantage of the cmos thresholds (trigger point) and require only a digital input.

This al;lows means that you do not have to calibrate the LDRs for the ambient light conditions.

I would add resistors above and below as a safety measure.
 
N

noise0

Member
Mycroft2152 said:
N,

You can save one pin by making the LDRs into a voltage divider. This takes advantage of the cmos thresholds (trigger point) and require only a digital input.

This al;lows means that you do not have to calibrate the LDRs for the ambient light conditions.

I would add resistors above and below as a safety measure.
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I tought to ldr voltage divider too
but it's no good because i want information about absolute light level too

for example: i am facing a certaini light... I do a 180? turn... more light or less light?
it's a stupid example to say that 2 adc give more "information" and tuning capability

anyway i think this breadbording session is enought... i'm goind to dirt my hands soon
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M

Mycroft2152

Senior Member
Sure, you will get more information about light levels from the LDR. But you will have the same problem that the mini sumo robots have.

You first need to determine the ambient light level on each sensor and then use those values to base your change values on.

It is just extra programming, unless you want your robot to go in circles...

Myc
 
N

noise0

Member
i can not see any programming complexity using 2 different ADC readings:

readadc pinADC1,b1
readadc pinADC2,b2

if b1>b2 then
else
and if

what is the problem with this ?
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D

Dippy

Moderator
Whenever someone disagrees with my methods (quite often) it makes me determined to prove them wrong...

As they say in the Restaurant Trade: "Don't talk - eat".

Have a go mate :)
If it works, be smug.
If it doesn't , keep quiet and learn the lesson.
 
N

noise0

Member
@Andrew:
oops.. typo

@Dippy
sorry, my english i too basic to understand what you say... you have to say me things like "the cat is under the table" or "The flower is red" ecc.. :)
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D

Dippy

Moderator
What I'm saying is: Try out your own idea. It may be perfect for your project. It shouldn't explode :)

I don't mean to say ignore suggestions as there is a wealth of experience on the Forum, but don't be scared to Have A Go.
 
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Mycroft2152

Senior Member
Dippy said:
What I'm saying is: Try out your own idea. It may be perfect for your project. It shouldn't explode :)

I don't mean to say ignore suggestions as there is a wealth of experience on the Forum, but don't be scared to Have A Go.
Click to expand...
Agreed, The PICAXE is a tough little chip. So you can try different things without too much worry. That's the fun of working with a PICAXE.

At the power levels generated by the solar cell, you have even less to worry about.

Go ahead and try different things and find out what works for you.

Myc
 
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