LDR circuit.. no luck :(

[KrisBlueNZ]

Maybe. There must be someone in your school who does electronics as a hobby... Could you put a note on a notice board somewhere?

 

[PhiLep]

There was one teacher that was a complete genius and knew every single thing about electronics but unfortunately he retired a month ago :/

I might try some of the physics teachers, they seem to have somewhat knowledge on electronics.

 

[(*steve*)]

There may be other options too. You seem to be in a very out of the way and isolated small town.

And also the same one that I'm in.

I haven't been following this thread as much as I might have. But I may be able to offer some assistance. I'll re-read this thread later when I'm not so busy and see what I can do...

 

[(*steve*)]

PhiLep, if my skype icon is active, try to get in touch with me.

I may be able to arrange something.

 

[KrisBlueNZ]

Thanks Steve. Feel free to start from scratch with the design. You might find it simpler to hack the LDR into the existing circuitry and sacrifice the low battery cutoff feature.

 

[PhiLep]

Thanks for all your help KrisBlueNZ, I'm going to try and find someone that can read schematic diagrams and help me out with this.

Which town are you in Steve? If you're going by my IP address (in Perth) that's probably wrong

I'm in the western suburbs of Victoria..

 

[(*steve*)]

Which town are you in Steve? If you're going by my IP address (in Perth) that's probably wrong

I'm probably wrong then.

Still, I've made the offer. Skype me and I'll see if I can offer you some direct help.

 

[PhiLep]

Do you think if I show the schematic drawing to Jaycar they will be able to tell me what resistors and stuff I need to buy?

also because the resistor readings may be incorrect, will this effect the LDR that I add in?

 

[KrisBlueNZ]

No, it doesn't matter if the resistor values are wrong in the diagram of the existing circuit. The extra circuit will still work.

Here's a parts list with Jaycar part numbers.
It covers everthing below the dotted line.

2x ZT2164 BC557 PNP transistor (Q1,2)
2x ZT2152 BC547 NPN transistor (Q3,4)
1x RT4360 trimpot 10k (VR1)
1x RT4354 trimpot 1k (VR2)
1x RR0596 resistor 10k (R9,11,12) (RR0596 is a pack of 8 resistors)
1x RR0608 resistor 33k (R10,13) (RR0608 is a pack of 8 resistors)
OR you could buy RR1680 which is a pack of 300 assorted carbon resistors ($7).
You already have the LDR, right?
You'll need a piece of stripboard: HP9540
You might want to get a track cutting tool: TD2461
You'll need solder: NS3008
You may need a soldering iron: TS1651 is their cheapest option, and it includes some solder and a solder sucker.
And you'll need some wire. Either 2-conductor or 3-conductor depending whether you put just the LDR remotely, or the whole new circuit remotely in a separate box. Putting the whole circuit remotely may be better for avoiding interference if the environment is electrically noisy. If you do this, put a decoupling capacitor e.g. Jaycar RM7125 across the supply rails at the remote circuit.

 

[PhiLep]

Thanks for that Kris!
I went out to Jaycar and purchased all of the stuff now
Going to give it a try now, I'll let you know how it goes.

 

[PhiLep]

Okay I have no idea where to even start or how to start :/

 

[PhiLep]

Okay so I had an attempt at putting it together, I don't understand schematics much so it is basically all guess work.

 

[(*steve*)]

OK, that's exactly upside down (the leads should stick through to the copper side, and turned around 90 degrees (the strips of copper typically run perpendicularly to most components. Added to that, you need a plan for how things are going to connect. You'll need to work that out first.

 

[PhiLep]

Those are the names of the components and where I placed them.

Some notes:
The guy at Jaycar forgot to give me two of each of the transistors. The photo above shows (in brown texter) where I will place the other two (Q2 and Q4) when I get them.

They also didn't have any stock of RT4360 trimpot 10k (VR1) but instead gave me 500ohm Horizontal Mini Trimpot - Open Carbon Type and said that it will be the same. Will this not work because of the replacement?

Also the LDR is just there for now but I will fix it up or make it remote when I put it all together.

I just need to know if what I have done is roughly correct and if it will work.

If it is all good to go how I have set it up, I'm assuming I would need to etch some sort of conductive pattern into the board? I bought the "Tool Spot Face Cutter" but have no idea how to use it or what pattern I would etch into the board.

Thank you so much for your help, once again and sorry for my lack of electrical knowledge

 

[KrisBlueNZ]

In addition to what Steve said... Google stripboard layout software
There are several alternatives. It's probably worth using a program to design your layout. The web pages you find should also describe the general principles of laying out your board.

You won't need much board area. There's no point using up the whole piece of stripboard.

Resistors are not polarised, i.e. you can connect them either way round. Trimpots have a wiper and two ends, which are marked CCW (counter-clockwise) and CW (clockwise) on the schematic. Transistors have three leads that need to be connected correctly. You can get the data sheet from the manufacturer's web site (fairchildsemi.com, onsemi.com etc) or the Digikey site - search for the part number, scroll down to the table of matches, scroll full right and click the 'D' in a box.

No, a 500 ohm trimpot is not suitable. I don't know why he told you it would be.

It's not roughly correct yet, not at all. You need to design a proper stripboard layout. Start by putting the components on the other side!

The spot face cutter is used to cut tracks where needed, according to the layout that you should design first.

 

[PhiLep]

This stuff is like rocket science to me :/
I'm trying to use DIYLC to make a layout, I'm not understanding this CCW and CW stuff..

 

[KrisBlueNZ]

OK. I'll see if I can come up with a layout using DIYLC.

I tried the other stripboard layout programs and none of them are any good, for various reasons. Does anyone have a recommendation?

 

[(*steve*)]

I've never used a layout program for veroboard.

Here is a page that describes the manual process. I'm not suggesting PhiLep follows this, but a quick read will (perhaps) give him a good idea of what the process is, and how it works.

 

[KrisBlueNZ]

Thanks Steve for the link, that's very helpful.

I don't think DIYLC is up to the task either, so I've done a layout the old-fashioned way, on paper.

This drawing shows the board viewed FROM ABOVE. The copper strips are on the UNDERSIDE of the board, i.e. they're not visible. The components are mounted on the top side. The transistors are shown viewed from ABOVE, with their wire leads pointing AWAY from you.

This layout is 10 strips high (strips run horizontally from left to right) and 14 holes wide, but you should add at least 2 to each dimension for safety. You can start by cutting or snapping the board to size. I hold it over the edge of a table and press at one side until it starts to snap along the holes.

There are three track cuts, at coordinates D4, J5 and H7. Remember when you're making these cuts that the board is mirrored, because you're looking at the underside.

The component mounting should be pretty clear mostly. There's a short link wire near VR1 (you could just solder the tracks together underneath, but I'm showing a jumper for clarity). R12 mounts standing upright. Q4 has its emitter pin bent outwards a bit more than normal, so it skips a track (track B) and connects to a further track (track A). Q1 and Q2 mount with their flat sides towards the right; Q3 and Q4 are the opposite. This assumes you're using the BC5x7 parts. If you're using the 2N390x parts, reverse all the transistors (Q1,2 flats facing left and Q3,4 flats facing right).

The three connections at column 14 are wires that run to the existing PCB. Look at the circuit diagram of the PCB (at the top of my circuit diagram in my earlier post) and try to figure out where to connect these wires on that PCB.

Good luck!

 

[PhiLep]

Thanks for that, that was very clear and easy to understand (if I was reading it right..)

Here's what I've put together so far:

I snapped the board a few holes extra to provide room for error.

I put the 500ohm trimpot in place of the one that I will be purchasing tomorrow. I've also marked Q2 and Q4 in brown marker as I will add them in tomorrow when I purchase them.

I've marked the three connections to the PCB in blue.

Is it all good to go for the soldering stage?

I'm going to do the track cuts after I solder it.