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There’s the ‘pbsong(dot)com’ website and there’s a contact link on the left side of the page.
Or you can just add ‘pete(at)’ before the domain name and you should get through.
Essentially both male and female connectors are identical apart from the fact that they have pins or sockets. The chassis mounting dimensions are, or should be, exactly the same.
The same applies for lead end shrouds, they will accept both types.
The circuit should now look more like this with the diodes added to a 10.0 volt zener and the capacitor added to eliminate spurious triggering.
Ah,.. just re-reading your comments again, that 5K isn’t doing much is it?! This is because the zener ‘can’ handle 1 Watt but in this case it’s nowhere near that, so the actual current flowing is very small. That means that where I have suggested a 5K preset, to get enough adjustment it maybe should be increased to as much as 50K or more, or it’s still going to be pretty ineffective.
I think maybe I should get to bed earlier so that my brain is actually awake when I post replies in here! Haha.
Just do an internet search for my name,.. you will get my website with contact details and a whole load of other stuff I get up to with electronics.
Hiyah Venkatesh,
as I’m not entirely sure of the precise nature of the ‘monitoring system’ you are looking to apply this to, the possibilities are almost endless.
What most people use is a simple ‘surveillance camera’ which has an analogue output along what is called ‘shot-gun cable’. This is not to say that it goes bang, at least it doesn’t if it’s wired correctly, it is the shape of the cable in that it is two cables joined together that look, in profile, like a shot-gun barrel. One cable carries the power to the camera and has a twin wire core, the other carries the signal from the camera and is a screened lead. It has to be screened so that it does not transmit or pick up electrical noise.
If you do an internet search for these surveillance cameras, you may well find the ebay guide (A Guide To Choosing CCTV Security Camera Systems) which has a lot of useful pointers as to what to look for, depending on your requirements. They have literally thousands of listings from a few dollars to hundreds of dollars, it really depends what you are looking to achieve and in what sort of environment.
I often think when trying to answer questions or repair a piece of broken equipment, that it would be very handy to have a crystal ball in my toolkit. Unfortunately, they seem to be unavailable, or the ones that are, don’t work! Thus I can only make a guess and suggest that you opt for an analogue output and hard-wire it to the monitoring system.
As this is obviously some form of security I cannot expect you to publish here all the details, or the system would be rendered public knowledge and the whole point of CCTV security is that it remains private.
I don’t sell this stuff but I do use it a lot. Not only for security but also I have two cameras in the back of the truck to give me rear vision when reversing, I also have what has become known as a ‘road-cam’ which is a small camcorder that records my journeys in a continuous loop of a few hours duration. If there was some incident that required me to show what happened, such as a collision, it is easy to to just show that video. It also makes for funny clips of motorists doing crazy things that end up on youtube! Having one makes me a better driver as I really don’t want to be in one of those clips myself.
As you can appreciate, the applications are many and really varied. The best way to learn is to find the specification sheets on the internet for as many different devices as possible,.. then shut youself away and read all of them carefully. The way in which you build your system is only limited by your imagination, that is why electronics advaces so fast. There is always a new way to use existing technology and sometimes a small innovation can make a whole new range of products we never thought possible.
Hi Irfan.
I notice your comment here, “.. but in 10V zener fluctuates only a bit from 11.88 to 11.96” so if we look at that result, then the voltage drop across the transistor and LED is 1.88 volts isn’t it? That’s the voltage with R4 at a zero value or close as make no difference.
As we are aiming at getting a cut-off at 13.6 volts than we need to arrive at a value for the zener/resistor combination of 11.72 volts.
As we have found that making R4 a 5K variable and that gives just over 1 volt adjustment, we could then make up the right voltage drop from a 10 volt zener by adding two diodes (1N4001,.. anything silicon really) in series. Each diode has a forward voltage drop of 0.6 volts (actually between 0.6 and 0.7 but always give as the ‘worst case’) and that would then make the effective zener+diodes a value of 11.2 volts, the 5K can then be used to trim the extra 0.7 volts and you should be in business.
In every case such as these where circuits don’t work quite as expected, it is neccessary to take a step back and look at what causes the error, then tweak the smallest number of component values till it does work. Adding series diodes to a zener reference is quite common practice because it gets expensive for equipment manufacturers to specify odd values which are not produced in such large numbers.
I would also add the 100nF capacitor from the junction of the diodes and R4 to 0 volts to be certain you will not get random variations due to noise. Zener diodes are electronically very noisy devices as they approach the point where they start to operate.
Oh yeah, if you were to search the internet for my name (this is my real name too), there is only one of me and you will find the website with contact details, and all kinds of other stuff I get up to!
Hi there, it seems you haven’t had a answer yet!
Two things come into play here. the first is the specifications of the crystal reference you are using, some are very stable with quite high temperature variations, others have less tolerance.
The circuit you put the crystal in will also be a major variable depending on the stability of the components. Particularly any tuning capacitors as these tend to not like anything much above 30 degrees C. It is possible to obtain components with high temperature stability but they tend to cost a lot more.
One solution is to mount the devices in a box that is also a heat-sink and use a small cooling fan.
Unless of course you are planning a voyage to the sun, in which case it’s all going to get toasted!
Hi Ashwini,
I think what you are trying to get is two isolated supplies off a single transformer?
It is technically possible by using a transformer with two separate, isolated secondary windings. Then separate voltage regulator circuits such as LM317 (variable) or LM7805 and LM7812, which would give isolation of both the positive and negative side of each output.
You would need to have something like a 0 – 12 + 0 – 12 transformer with a full bridge rectifier on each winding.
It’s an odd configration but one which used to turn up on old televisions to keep the HT circuits isolated from the rest. Basically we didn’t want to be touching anything remotely connected to 25KV,.. because it hurt!!
Not quite sure how far back you are going in history here! The original analogue camera is the one that uses film but that is not exactly what you are looking for here is it?
Basically, all electronic cameras are based on what is known as a CCD (Charge Coupled Device) and those are tiny circuits that are sensitive to light and in the colour versions, they also pick up the levels of red, green and blue light separately. The size of the chip physically, is not always a good indication of its sensitivity but generally cameras are now graded by the number of pixels they render from the image. It is that information that is digital and then processed to give a required output which could (and often is) analogue. Thus all electronic cameras are digital at the ‘sharp end’, that is the bit that does the sensing because light is actually an analogue waveform, the chip is an ADC (Analogue to Digital Coverter). For your purposes it would be best to have at least 5MP (Mega Pixels) if you want clear images although for close range you may get away with as little as 2MP
The output from a camera can be in digital or analogue format and most that are easily available are analogue output, often including a small microphone, with separate leads for audio (white plug) and video (Yellow plug) plus a power connection. It is possible to get wireless versions but the batteries tend to not last very long and as the whole purpose of a security camera is for it to be difficult to see or tamper with, changing batteries becomes a real problem! It is better to go for a hard-wired system. More expensive versions are split RGB and that can be either in standard analogue or digital, it all depends how much money you have to spend or burn!
For security monitoring, you really need to have a camera with the lowest possible ‘LUX’ rating. This is the camera’s ability to pick up images in low light and also they should be sensitive to infra-red light (IR) at fairly low level. All CCD chips are in fact sensitive to IR but not all do it well. Some cameras are now fitted with a halo of IR LEDs that are effective up to maybe ten meters but if you want to have better range than that at night, there are also IR LED flood lights that make the images look like it was daylight.
The lense is also a major factor. As in any photography, TV, Film etc., a good quality lense will make a lot of difference to the images but having said that, a pin-hole camera for short range is often perfectly adequate, I would use them up to 5 meters but much further than that, face or number-plate recognition requires some magnification and precise focus.
Bottom line? For cost effective monitoring, a good CCTV camera with a LUX level of 0.5, IR LED illumination and a simple video/audio output for a small area will give you a similar quality image to a basic computer web-cam. in fact, that is a digital output at the bottom end of the market and I have seen them used as simple shop CCTV cameras. If you want to use multiple cameras there are add-on boards for computers that will take the analogue camera inputs and record all at the same time. To be honest, it is better to get a dedicated recorder though. Again, here there are variations. Some record in AVI format which takes up a lot of disc space and some in MPEG which takes less space and gives more recording time. Then or course it is possible to have an analogue recorder using VHS tapes but the biggest problem with those is that people tend to re-use the tapes and quality falls dramatically to a point where the recording is pretty useless for any means of indentification. The heads wear, the tapes wear and the cost of maintenance is high.
It’s all really a matter of what the budget avaiable will afford. BUT just spending a lot of money on a top name brand does not mean you get the best quality or best value! Shop around and read the specifications carefully.
Hi Irfan. Ah,.. oops!
I did say that I thought the voltage of the zener used here might be wrong as it looks like the original schematic was generated by a computer program. In my long experience (40 years), I have found that all the theory in the world develops some very strange habits when we let it lose in the wild.
I have a looked at this schematic again and as the forward voltage drop on a red LED is approx 1.6 volts and the voltage drop from base to emitter on the transistor will be 0.6 volts, (due to the minute current the resistor is not doing much) then the zener then should be,.. 13.8 – 0.6 – 1.6 = 11.6 volts. Now that is a very odd value and I suggest making the zener 10 volts with the resistor R4 a 5K preset potentiometer, then adjust it till the circuit shuts off at the suggested ‘float charge’ level of 13.6 volts which is standard for all lead-acid bateries, or just a little higher than that. It is possible to charge to a higher voltage but that may also cause the battery to heat up and shorten its working life-span. I’m not saying that the circuit goes into a float state, it shuts off completely at the max value you set.
You also mention that putting your finger on the end of the zener causes the circuit to switch off. Yes it will.
This is because our bodies operate with electrical impules in the nerves that are actually a lot higher than some might think. Add to that the fact that we also pick up any mains interference like an aerial, thus what is happening is that our bodies generate quite enough voltage to interfere with a simple base junction in a transistor! This is the buzzing noise you get if you touch the input lead to an audio amplifier. It is also why sensitive electronic components are packaged in anti-static bags and foam.
If there is a lot of electrical noise in the envoronment (remember there is a mains transformer very close), adding a capacitor of around 100nF from the bottom of the zener to 0 volts should dump that noise and stop EMI (electro magnetic interference) from triggering the transistor at random.
Just to be certain, as I have just had a delivery of 10 x LM317 chips, I will dig out some bits tomorrow and actually put this circuit together myself to pinpoint where the computer that originally designed it, got it so wrong. I will update the schematic accordingly.
I agree with AJISH ALFRED here, you haven’t given us a lot to work with really.
If you require just 50% of the voltage, a simple on-off-on switch can be wired so that in one ‘ON’ position the battery is connected straight to the load and on the other ‘ON’ terminal, you could put a pair of resistors as a voltage divider to give you half the voltage.
BUT, in that simplest of configurations you would also be dumping half the power to the 0 volt line too, which is going to drain the battery just as fast at full power.
The best way to do this would be to use the LM338T voltage regulator which is capable of handling 5 amps and use the switch in the adjustment circuit. If you find the free ‘Texas’ datasheet from one of the many places online, there are several application notes you could calculate this from.
If you want current control, that same chip can achieve that function too. If you want to do both,.. yes that is also in the datasheet.
By using an adjustable voltage regulator, any switch can be fairly small as it is only handling low current. Switching 4 Amps will mean a much more expensive switch as the contacts will have to be a lot heavier. I think you may find a small switch and a handful of components may work out a cheaper option, as well as being more accurate, more adaptable and have a longer service life.
This circuit is from the datasheet and could be configured very easily to give you what you need.
Ah,.. Sorry, I forgot to check that side of the schematic didn’t I?
The centre-tap of the transformer connects to the 0 volt line and I would suggest that the charger (low volts) circuit is ISOLATED from the case entirely. This ensures that accidentally dropping the live lead on the box does not burn something out.
Certainly connect an earth point to the case to prevent any mains failure from making the case live.
So, the circuit should now look like this,… with your 18-0-18 transformer you should then have a positive line of 25 volts DC, in which case C1 should have a working voltage higher than that and I tend to allow for transients 10 volts above so it would be 470uF, 35 volt working at least.
Ah,.. Sorry, I forgot to check that side of the schematic didn’t I?
The centre-tap of the transformer connects to the 0 volt line and I would suggest that the charger (low volts) circuit is ISOLATED from the case entirely. This ensures that accidentally dropping the live lead on the box does not burn something out or frighten the life out of you with the spark.
Certainly connect an earth point to the case to prevent any mains failure from making the case live.
So, the circuit should now look like this,… with your 18-0-18 transformer you should then have a positive line of 25 volts DC, in which case C1 should have a working voltage higher than that and I tend to allow for transients 10 volts above so it would be 470uF, 35 volt working at least.
Ah,.. oops! Sorry, I forgot to check that side of the schematic didn’t I?
The centre-tap of the transformer connects to the 0 volt line and I would suggest that the charger (low volts) circuit is ISOLATED from the case entirely. This ensures that accidentally dropping the live lead on the box does not burn something out or frighten the life out of you with the spark.
Certainly connect an earth point to the case to prevent any mains failure from making the case live.
So, the circuit should now look like this,… with your 18-0-18 transformer you should then have a positive line of 25 volts DC, in which case C1 should have a working voltage higher than that and I tend to allow for transients 10 volts above so it would be 470uF, 35 volt working at least.
