cliffclavin

Hello all! At work we have a closed circuit television system. It is a very cheap kit! The CCTV camera (composite video feed) is fed into a rf device, so the CCTV camera is viewed through a TV arial type connection (not rgb/composite) This is plugged into the arial circuit used to pick up terestrial television signals. The upshot of this is any television connection to the arial system can receive terestrial tv signals, and the cctv feed, depending what channels it is tuned to. We would like to add an audio channel to complement the CCTV, so anybody watching CCTV would hear our soundtrack....he he he We tried re-tuning the output of an old VCR (video casette recorder) to the same frequency as the cctv rf device, plugging it in to the arial 'system' and seeing what happened on the TV. The vcr and cctv competed for signals, and only the audio was avaiable to hear (with a lot of distortion). So my question is: How can we *reasonably easily* add an audio track to the cctv via the arial system? (not at the rgb / composite side) Can a VCR be easily modified to only output audio signals? Can a device be built / exist that allows me to do this? I see soldering 'kits' are available, that plug into a TV, and emulate old games (such as pong or space invaders). These produce the kind of signals I want (sadly video not audio...) Many thanks in advance! N.B Work is owned by a life long friend, only six of us work at the premisis. This is meant as a joke -this isnt nefarious!

Hello! I would like to monitor the voltage from a sensor. The sensor produces 0 to 10 volts. I would like the display to show the voltage in relation to a scale of 1 to 2000. eg. 0v = 0 2.5v = 500 5v = 1000 7.5v = 1500 10v = 2000 The digital voltmeter project can be modified to measure a voltage range of 0 to 20 volts by replacing R3 with 120 Kohm 1% res. (Voltmeter project link) http://www.electronics-lab.com/projects/test/014/index.html Now if I took the voltage output ( 0 to 10v ) and put a voltage doubler there to make the sensor output 0 to 20v, and connected this to the input of the modified range voltmeter ( 0v to 20v), Will the voltmeter display the range I want from the input voltage? I guess I'd have to disconnect the decimal point LED in the display ( so 12.15v would read 1215 ) Will this do what I want? Many thanks ps. There is a long forum discussion about making the voltmeter http://www.electronics-lab.com/forum/index.php?board=2;action=display;threadid=119;start=1;boardseen=1 This posed a few questions that I couldn't find the answer for. However, it was a long read (10 pages) so could somebody who's built the voltmeter answer : How stable is the device? Somebody said as the voltmeter 'warms' up, the volt reading changes. Is this true? By how much? Could someone who's built this explain a bit more? Will the voltmeter (when modified to 0 to 20v range) read to 2 decimal points (eg. 12.51 v ) ? thanks

Hello! I would like to monitor the voltage from a sensor. The sensor produces 0 to 10 volts. I would like the display to show the voltage in relation to a scale of 1 to 2000. eg. 0v = 0 2.5v = 500 5v = 1000 7.5v = 1500 10v = 2000 The digital voltmeter project can be modified to measure a voltage range of 0 to 20 volts by replacing R3 with 120 Kohm 1% res. (Voltmeter project link) http://www.electronics-lab.com/projects/test/014/index.html Now if I took the voltage output ( 0 to 10v ) and put a voltage doubler there to make the sensor output 0 to 20v, and connected this to the input of the modified range voltmeter ( 0v to 20v), Will the voltmeter display the range I want from the input voltage? I guess I'd have to disconnect the decimal point LED in the display ( so 12.15v would read 1215 ) Will this do what I want? Many thanks ps. There is a long forum discussion about making the voltmeter http://www.electronics-lab.com/forum/index.php?board=2;action=display;threadid=119;start=1;boardseen=1 This posed a few questions that I couldn't find the answer for. However, it was a long read (10 pages) so could somebody who's built the voltmeter answer : How stable is the device? Somebody said as the voltmeter 'warms' up, the volt reading changes. Is this true? By how much? Could someone who's built this explain a bit more? Will the voltmeter (when modified to 0 to 20v range) read to 2 decimal points (eg. 12.51 v ) ? thanks

Hello. I am hoping one of you smart people could help answer a question for me. I am nearly finished building a three stage timer/ controller out of CMOS 4000 series IC's - I have built & checked each section of the circuit, and it works ok! A 4093 Schmitt Nand Gate provides clock pulses to some 14 other 4000 series chips. The power is 9v dc from a battery, but I will upgrade to a transformer when its completed My question is about power requirements / dissipation for the circuit. I have attached a pic from the 4017 datasheet, which shows the power dissipation requirements for the 4017. Could somebody please look at the calculation and tell me the power requirement for the 4017, and how you worked it out - so I can work out the power requirements for the other IC's in the circuit. The formula is : Typical Formula for P (uW) at 10v dc 2200 Fi + SUM OF (FoCl) x Vdd2 where Fi = input freq (Mhz) Fo = Output Freq (Mhz) Cl = load Cap (Pf) SUM OF (FoCl) = sum of outputs Vdd = supply voltage This is so the power supply has enough power, and so I can work out a value for a fuse. Any takers ? Who's able to explain how to work this out?

Thank you so much for taking the time to help me! I am glad that the circuit will work as I had hoped! will using D Type Flip flops work instead, only because I have made the order for components already... It seems a shame to place another order for one Dual RS flip flop costing 49 pence. The postage alone will be five times that!!! The circuit I have shown here is a simplification of my idea, just to test the idea that 2 flip flops can cycle between three delays. Instead of using one counter for each delay, I intend to use several counters in series for each delay, connected via logic 'And' gates and switches, to select a delay.. eg. Clock 1hz. 2 decades counter connected together , the 10 + connected to the Clock in of the next. Counter 1 will have outputs 0 to 9 connected to a 1pole 10 way spst switch. Counter 2 will have outputs 0 to 5 connected to a 1pole 6 way spst switch. The two switch outputs are connected to an 'And' gate, whose output is connected to the flip flop. Sorry for the pic - am terrible with mspaint! http://cliffclavin.myphotoalbum.com/view_photo.php?set_albumName=album05&id=timeselect Using this method, (lots of decade counters and 6 various input single pole switches) the following time periods are selectable: Delay One = 1 to 70 secs Delay Two = 1 to 100 mins Delay Three = 1 to 30 mins (Actually the circuit in the diagram above would produce a selectable time period of 11 to 70 secs. (minimum setting switch one = 1 sec, minimum setting switch two = 10 sec). I will connect lead 0 of the spst switch to the clock, load 1 of the switch to pin zero of the counter to achieve a 1 sec delay when both switches are set to there first setting etc. But this isnt shown for clarity - I was just showing my method of using switches, 'And' gates and counters in series to produce set delays of varying magnitude around the flip flops.) That is why I have gone about this in a complicated way, so I can have an accurate, cycling, three stage selectable delay timer, with delays in the above range. Wow, what a mouthful! Out of interest, does the 'other' idea (not using flip flops) also work, if you connect +5v to the enable in your simulator? Can you see an easier method to do this (and cheap - the components bill was 15 pounds but I already had a few...) Again, thank you for taking the time to help me! Cliff [Edit] Because the Clock input of the flip flops will be connected to 0v, I guess I can still use the Dual D Type Flip Flop and not have to order a Dual RS FlipFlop. Correct me if I'm wrong here....

Alun, thank you very much for taking the time to help. Pity the second soloution does not work - the schematic you provided was accurate. However, the last schematic posted (my first idea with the flip flops) has a problem? Just to clirify my desin involved using D- Type Flip Flops. You have connected the Reset of the first Flip Flop to a Clock. Does the Reset of the Flip Flop (s) need to connected to the clock? There is a specific Clock input (for the D Type) However, my first (and working!) two stage timer uses a D- Type Flipo Flop to cycle between two delays. I just used the Set / Reset pins and connected the clock input.to 0v This design (Three stage timer) involved a Dual D Type Flip Flop, so I was gonna connect both Flip Flop Clock input to 0v, and use the Set/Reset pins, not using the Clock at all for the flip flops. When you tested the circuit in its current format (with the erronious clock => reset connection, which side of the circuit stayed on?) Would you be so kind as to see what happens without the clock connection to the Flip Flop reset? Many thanks again for your help, Cliff

I have drawn a clear diagram showing the above suggestion. http://cliffclavin.myphotoalbum.com/view_photo.php?full=1&set_albumName=album04&id=timer999 It looks ok, but I have a question regarding counter three triggering counter one. When the 10+ pulse comes from Counter Three, ithe pulse goes to Enable of Counter Three, So a steady signal holds Counter Three steady at 10+. This steady signal is sent to the Reset of Counter One. Doesnt Counter One need a short pulse to the Reset pin? Will the constant on signal from Counter Three hold Counter One in Reset Mode ?(Holding at Zero?) So the upshot is the circuit would cycle through the three delays, then be held on permanent hold at counter one? Or will the circuit cycle through the three delays continually?

Kevin Weddle : No offence taken - I am just a tad frustrated. :) :) :) I am re-working the diagramn to try and make it more readable. However, an alternative soloution has been suggested without the use of the flip flops. What do ya make of this ? : One way is to utilize the enable input of the 4017. If the desired output is connected to the enable input, the counter will freeze when the output goes high. It can released only by reset (in what situation is starts counting from zero). So first counter's output is connected to it's enable input and second counter's reset via an inverter. Then the first one's output is low until the counting reaches the selected output (it goes high the). Enable makes the counter freeze and releases next counter to count (not in reset situation any more). While the next counter is counting the third is held reset until the second counter reaches the seleced output value. Then 2nd counter freezes and third is released for counting. When the third reaches the selected count, it will reset the first counter (no inverter here). The outputs for the relays are formed by combinational logic from the counter outputs. ' This sounds like a very elegant soloution. What d'ya think? Better than my original? Many thanks, Cliff

Kevin Weddle : Sorry that looking at the design makes you dizzy! Thats why I wish I had electronics workbench at my disposal. OK, I will try to make the diagram more readable. The only way I know how to use D-Type flip flops is in the bi-stable mode (toggle bistable / toggle flip flop) Do you have anything useful to say? I am trying and am here for help, you just told me my diagram makes you dizzy, it is a mess and you don't like the way I've implemented the flip flops. I thought using D Type flip flops in bistable mode was fine. It is listed under the basic uses of a d type flip flop here http://www.doctronics.co.uk/4013.htm Could you explain this a bit more, or giva a link I think the design is quite simple: Timer A finishes count, sets flip flop a.. Timer B finishes count, sets flip flop b. Timer C finishes count, Resets flip flops a & b Timer A starts count......... A friend checked the diagram and queried whether Counter 3 (timer 3) would be able to Reset flip flops a and b at the same time. He also suggested a fix if this was the case. What do you all think, can Counter 3 Reset both flip flops with the same pulse? Thanks Cliff

Thank you taking the time to reply - I will look into the CMOS 4538. Thanks for ya advice about interference - your post sounded like a knightmare trying to remove interference! The circuit will be powered by 12v dc - one of the reasons I chose the 4000 series of IC's was the 'lack of inteference' at 12v etc I already have a prototype using two binary ripple counters and a d type flip flop (all 4000 series, up tp 17v) driven by a 555 astable. This functions perfectly and is the inspiration for this 3 stage timer. Do you think my design will perform as expected? I am buying the parts today so fingers crossed!

Hello I have some experience building electronic kits as a kid - radio's, transmitters, amp's etc. Later at University I was taught aspects of digital design using Electronics workbench - such as logic gates, flip flops, binary adders etc I have a basic working knowledge but with some gaps. My main problem is I do not have electronics workbench or university lecturers handy to help... I am trying to build a simple timer that cycles between 3 set delays, while energising two relays. One relay is on during the first time period, and the other relay is on during the last time period. My idea is to use both sides of a D Type Flip Flop - and use the 2 flip flops to cycle between the three time periods. And use three 4017 Decade counters, and a 555 astable for clock pulses. A capacitor & some diodes will 'set' both flip flops in the approprate mode on power-up so they are in sync. This is not shown on the diagram. My idea: Counter A starts count. Relay B is on Counter A finishes count, resets flip flop A, Relay B is off. Starting Counter B. Counter B finishes count, Resets flip flop B, Starting Counter C, Relay A turns on. Counter C finished count, Sets Flip Flops A and B, Relay A turns off. Relay B Turns ON, Counter A starts count. I have drawn a diagram of how I think this would be connected. I have only included connections for the logical side of things (Path of the clock pulses) I have only shown one output leg on all three 4017 counters for clarity. http://cliffclavin.myphotoalbum.com/view_photo.php?set_albumName=album03&id=timer1 Any help is much appreciated. Self education can be such a head ache! Will this work as I expect it to? Any ideas welcome! Cliff