Editing a Biss0001 PIR circuit + connection to 18m2

Steve2381

Senior Member
Hi all.
I am playing with a Biss0001 PIR controller chip (found one in the workshop).
I would like to connect it to an 18m2.

My thoughts are to lose the 1M 'time' pot on pin 3, thus leaving it set to minimum 'on' time. I can then deal with the timing using the Picaxe.
Set pin 1 high - which is retriggerable mode.
Connect output pin 2 directly to the Picaxe.
The Picaxe will have a relay output. Basically the Picaxe is controlling the timing after its been triggered (plus lots of other features - eg, a DS1307 etc).

But... there is a 1M pot on pin 12 that controls the sensivity. How can I control this pot/input/feature using the Picaxe?

My original thought was to use an AD5242BRZ1M digital pot. But these ain't cheap and I was wondering if I was missing a much simpler method?
http://docs-europe.electrocomponents.com/webdocs/0700/0900766b80700a24.pdf

Thanks for any assistance
 

Steve2381

Senior Member
Oh... thought it was attached.... here it is...

That circuit diagram above shows the supply as 3.3v. I will run it at 5v.
 

mikeyBoo

Senior Member

JimPerry

Senior Member

AllyCat

Senior Member
Hi,

The second "Pot" appears to be just changing the effective resistance value from 470k up to 1M5. Another (CdS2) LDR (inside a light-sealed enclosure, with a LED) might achieve that reasonably well (but 1M is quite a high value). Drive the LED (via a resistor of course) from a PWM pin and check/adjust for suitable sensitivity, range and linearity.

Cheers, Alan.
 

Steve2381

Senior Member
Thanks guys.
I have those 'pre-made' pir modules here already. They are based on the Biss0001 chip anyway. I am trying to get the footprint down so it would be nice to make a new custom pcb with all the IC's mounted on that (18m2, PIR controller etc).
I suppose I could 'hack' one of the pre-made modules.

I have found a supplier of the digital 1M pots for a reasonable amount. Do you foresee any issues using one of these digital pots?
Really don't want a servo. The LDR might work in theory.
 

Steve2381

Senior Member
Is it only X2 parts that have I2c? I have a pile of M Picaxes here and no X chips.
I thought 14m2's had I2c (SDA on pin 9 and SCL on pin 10)? I have searched and can't find any examples of 14m2 I2c programming

Ok... I'll edit that. They do have I2c.

I am really struggling with the programming of this I2c comms with the digital pot - AD5242BRZ1M. This is what happens when you don't program for a while!
 

Steve2381

Senior Member
Yes... any assistance on the HI2CSETUP command and the required HI2COUT command for this digital IC would be greatly appreciated.... just not getting anywhere here.
 

Steve2381

Senior Member
HI2CSETUP I2CMASTER, %01011000, I2CFAST, I2CBYTE
HI2COUT %10000001, (%00000000)

What am I mising? I have a 14m2 with the SDA on pin 9 and the SCL on pin 10 (both held high by a 4k7).

The First set of numbers is the part address (I have both the address bits tied low).
The second set in the Hi2cout command is the Instruction byte... which is basically not needed... the only one I am using is the first '1' that selects the second side of the digital pot (RDAC2).
The third set of numbers is the data... which should set it to 0?

I obviously don't understand how this works...
 

hippy

Technical Support
Staff member
How are you determining it doesn't work ?

Perhaps post your full code and a photo of your wiring in case there are any connection errors. It is always best to start with I2CSLOW then increase I2C bus speed once that is working.

You could try toggling the O1 and/or O2 output pins which will confirm the I2C is working.
 

Steve2381

Senior Member
Well I have a multimeter across the resistive output teminals. It is showing 0.5M which is the switch on default reading.
I will try a photo... although not sure that will be easy to work from
 

Steve2381

Senior Member
Well as an update... I have the digital pot working. Turned out that 50% of the IC doesn't work. Its a dual pot and the other side works ok.

The Biss0001 PIR sensor IC is breadboarded and working as well (Circuit diagram in the first post).... however, it is suffering slightly.
The 1 Meg pot does alter the sensitivity (its a standard turn pot - not the digital one yet), but the PIR output is 'on' for nearly all of the pots resistance. Only the last 10% actually works as a PIR.
Any ideas? Its built on a breadboard.... do you think its stray signals? Or perhaps something in the circuit needs altering from the recommended values (what that would be, I have no idea).
The supply is clean and smoothed, so I don't think its a supply issue.

Edit.... well as usual, you spend an hour looking and the moment you post in the forum, you find something...

Its the HC-06 bluetooth receiver that is also connected to the circuit (Pir output and HC-06 both connect to a 14m2). Supply is separate and has 100uF + 01uF capacitors, so I not sure what is causing the issue.

I have 3x 7805'S running this circuit which is total overkill really. What am I missing when it comes to running modules off these 7805's? The only way I seem to be able to get a clean supply to each part is with its own regulator.
I usual throw an 0.1uF and a 100uF across the outputs to smooth the supply (capacitors already on the incoming side). Is there anything else I can try?
 
Last edited:

sages

Member
Maybe the Bluetooth radio transmitter is transmitting as designed and the PIR is detecting the RF directly and not via any copper connection.
Just because the Bluetooth radiation is intended doesn't preclude it from causing interference.

I'd suggest trying to physically separate the PIR and bluetooth modules, maintaining the supply bypass close to each module to see if it's direct interference.
 

Steve2381

Senior Member
Its the supply. I have the Bluetooth module in exactly the same place, but now on its own 7805. The problem has ceased.
 
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