You are going to have some serious static problems with your aluminum laced carpet. You will most likely send some severe spikes down your line.

I understand that problem... Hence, I want to be very sure if the given system works...

I have a question.

I have been following along for a while now, and there is something I have to know.

What is the requirement for the project?


Was it: Find a way to detect a persons placement in a room?

Hello ... no, initially, the project was meant to detect a person falling on a given surface... but, now because of some reasons, I am restricted to detect the presence of a person in a room.. And the way I am doing this is with a carpet
with sensors underneath.

I had a very similar project a decade ago, and we built the room (12ft x 12ft) and had to show a persons movement through the room.

Is the point of the project to deal with frequency filtering and parasitics?

 

Hello,
I had another question.. SgtWookie, I remember you telling me a voltage splitter circuit..

I tried it out, but, it did not supply enough current to drive the buffers, muxes, precision rectifier and the micro-controller unit..

Hence, I thought of using this particular IC ICL7660... However, I dunno what is the maximum current capacitor of this chip...

I tried connecting 8 buffers, 1 CD4051, 1 CD4052, 1 precision rectifier and the micro-controller unit...

Everything works simply awesome... However, I am bit nervous to use this chip to drive 32 buffers, 4 CD4051, 1 CD4052, 1 precision rectifier and the MCU...

Do you think this chip will suffice to the current needs of the circuit... I don't think this circuit will demand much current...

I am having a power supply of 12V with maximum current output of 1A... I used it previously to drive 21 precision rectifier circuits...

I am thinking of using the same power supply or a simple adapter(something like a cell-phone charger) having +12V output voltage...

 

The ICL7660 is a low-power charge pump. It will add noise to your power rails.

I don't know what you used for your rail splitter, but perhaps it was a "weak" opamp. An L272 would likely take care of the problem.

 

The ICL7660 is a low-power charge pump. It will add noise to your power rails.

I don't know what you used for your rail splitter, but perhaps it was a "weak" opamp. An L272 would likely take care of the problem.

Yes, I used L272... inspite of that, I could not see efficient performance... I gave 14V input, and the output was connected to 7805, but I failed to observe +5V at the output of the 7805...

 

Can you post a schematic?

 

Where is your schematic?

 

hI,
please check the attached document. I have made the circuit in PCB Artist... software which I used to layout my PCB. Its a .sch file, should open with ORCAD I guess..

 

Please convert it to a .png format file using Alt+PrtScreen and pasting it into MSPaint.

I have PCB Artist installed, but you used a newer version and the version I have won't read it.

 

Please convert it to a .png format file using Alt+PrtScreen and pasting it into MSPaint.

I have PCB Artist installed, but you used a newer version and the version I have won't read it.

The circuit is too big enough to fit into the screen... damn... wait.. i will find some solution or else, shall redraw...

 

Just show the section where you have the power supply and regulator.

Please remember this is strictly a "G" rated forum. Keep the language clean.

 

Just show the section where you have the power supply and regulator.

Please remember this is strictly a "G" rated forum. Keep the language clean.

Ok, sorry about that...
I have attached the .jpg file.. Please check and let me know if that is clear enough....

 

Well, you are using a 7805 and a 7905. That means you'll need at least 15v input with NO ripple voltage.

Each regulator has a minimum voltage dropout of 2v, but that increases at higher current.

You could also replace the 7805/7905 with LDO regulators.

[eta]
I don't see any caps on the inputs or outputs of the regulators. They are mandatory.
I don't see any bypass caps on any of your ICs. They are also mandatory

 

Ok, How about this chip... . NMH0509DC... i know its costly... but it has like 111mA of output current....

 

I'm not going to do this - you find a regulator, and me give a yay or nay.

Why don't you simply use a plug supply that is more than adequate for your power requirements and regulator dropout?

If you use a switching DC-DC converter, you will add lots of noise to your power rails. Is that what you want to do?

 

I'm not going to do this - you find a regulator, and me give a yay or nay.

Why don't you simply use a plug supply that is more than adequate for your power requirements and regulator dropout?

If you use a switching DC-DC converter, you will add lots of noise to your power rails. Is that what you want to do?

hmm... Well, I don't want to add noise to my power rails, but, I definitely want to use a wall plug adapter... Hence, so much of curiosity. I want to make my system such that I can carry the electronics anywere, plug in an adapter and whoooosssh!!! it works

 

Hello All,
I am into the final stages of the project... I have built a carpet 12feet x 12feet... connected wires and all... everything is ready...

Now, as i mentioned previously, I have 32sensors going into a PCB, which consists of 32buffers (TL084CN), the output of which is given to 4 8:1 CD4051 mux..

the output of the all the four 8:1 mux is then given to 1 4:1 mux (CD 4052), and the output of this 4:1 mux is given to a precision full wave rectifier(TL084 ) circuit... all the select lines of the mux are selected by PIC microcontroller 18F series

I am facing a new problem...

When I connect each and every input signal, it works, I tried connecting 16 sensors at a time, even then everything works perfectly...
However, when I am giving 32sensors, only the last 8 don't work...

Is the circuit loading? I am using NMH0509SC as power source which is providing power to all the 32 buffers, 4 CD4051, 1 CD4052, 1 precision amplifier and also to the microcontroller unit...

I checked the amount of current the whole system is leaching from the power supply, it is approx 400mA ... ( this is mentioned in the datasheet of the NMH0509SC that it requires atleast 500mA) ...

Do you think that the whole circuit is too big to leach enough current?

What can I do?

 

You can try using separate power supplies to each problem having IC.

But this sounds like a wiring problem. or you may have a faulty MUX.. Check the mux of the 8 that DOES NOT work alone to see if it is getting and giving proper signals alone.

 

WHY are you using TL084's? They are noisier versions of the TL074's, which I told you before were not good to use in your application.

They do not have rail-to-rail inputs and outputs, and use more power than the other opamps I suggested.

 

You can try using separate power supplies to each problem having IC.

But this sounds like a wiring problem. or you may have a faulty MUX.. Check the mux of the 8 that DOES NOT work alone to see if it is getting and giving proper signals alone.

I have 4 such sets of 32 sensors, and I observe same behavior in all of those..
Also, I checked the wiring for all... It seemed ok.

 

Try disconnecting a different set and reconnecting the set that won't work.

If the set that won't work now works, you have a power supply loading problem.

Seems to me that you were marginal to begin with.