Jump to content
Electronics-Lab.com Community


  • Posts

  • Joined

  • Last visited


terramir's Achievements


Newbie (1/14)



  1. I understand that the voltage would change when the temperature is changed, there would be a pot that changes the base voltage at STP, but if the temperature rises (with a ptc in series with the rheostat (pot without using third leg)) the resistance on the base would of the shorting transistor would increase hence the transistor would short the Base current to the main transistor current at a higher voltage, this is intentional, because then the fans would rotate at a higher speed to bring down the temperature. the question here is not a reference voltage, because I dun care about that, these can be individually calibrated. the question is is there a way to make this circuit more efficient, cheaply like using an op-amp or a comparator to do the switching, as long as it's cheap, (op-amps and comparators can be had for less than a buck) I care about the over all efficiency. And I suspect this circuit may have problems with partial on states, which means loss of energy and heating of the mosfet, with one of those to I might just get discreet switching states. Unless I can choose a transistor for switching that has the tendency to turn on at a certain voltage let's say 0.7V but turns off at 0.68V then that would be discreet enough alright without going into op-amp's or comparators. I need suggestions, and I understand as well that the transistor heating up will make a difference as well, however this thing will be cooled by the same fans that are being controlled. terramir
  2. I'm not sure you exactly know what I mean I would be shorting very little current to 0V Maybe this will help envision what I had in mind Mind you where the variable resistor is there could be a resistor and a variable resistor as well as a PTC to regulate for temperature. you said something about an inductor I'm open to suggestions but I wanted to keep it as simple as possible while still burning as little energy off as possible and keeping it cheap. Let's say the adjusted value is 8V if the voltage at the capacitor is 8.2V it would trigger the shorting transistor and the main transistor would turn off, then as the capacitor discharges into the load the the voltage would drop, to let's say 7.8V and the grounding transistor would turn off. of course this is really simplistic but you probably get my drift. terramir Open to suggestions here, just want to keep it as cheap and simple as possible
  3. I was writing up a post on pwm after someone said that pwm didn't regulate voltage, and how before and after the filter capacitor the voltage is either 12 or 0V before but let's say 8V afterwards. This gave me an idea about a adjustable voltage regulator that would work sort of like this the transistor or a mosfet starts in an on state after a capacitor charges when the input turns on, however; another transistor shorts the cap to the ground, instead of letting it supply the base current, when a certain voltage has been reached after the first filter cap on the output. Basically when A certain voltage has been reached the main transistor or mosfet turn's off, when it goes below the threshold it turns back on this could be temperature controlled as well. What do you guys think? A. how wasteful will this circuit be I figure I can keep the waste down by using a high gain as the main transistor/mosfet, hence only needing a low current on the control part of the circuit? B. How far down can I narrow the hysteresis? C. is this circuit feasible with thermistor control, I figure I could up the voltage by using a PTC so the higher the temperature the higher the resistance to the shorting circuit so the voltage would increase as the temperature rises. What do you guys think could this be done simply and cheaply, what I would like to use this for is fans so I could let's say adjust the fans for 5V's but after a while if the temperature rises the fans would start spinning faster until the temperature drops. Please any feedback will be welcome :) terramir
  4. Not looking for pwm :( pwm wastes energy nothing else Matter of fact used one of them screwed up my lead acid batteries! Also I'm not trying to lose power here but gain it. There is a theoretical possiblility of using pwm and create a second rail that catches all the pwm dropouts and op-amps em back into the circuit, however the efficency of that is questionable at best. Solar panels are fail safe designs they are rated let's say 100 W but that's around 17V 5.9A however a 12V battery is mismatched so the battery will pull the voltage down to 12Vx5.9A = 70.8W well there's the greatest loss. Trust me my design is solid, except for how I'm gonna put this DC into a transformer most mppt's use audio frequency for it 20 to 80 khz to keep transforming losses down. PWM is great for charging on the grid, it will take the power it needs and well burn some excess in the process, however when you want to squeeze every mA you can get in charging current out of it pwm fails miserably.
  5. first dun cut any wires just yet, open it up and see what makes it tick, mechanically, and see what bumpers and stuff have switches to make the sounds and stuff. if you can move those switches into the new nice looking bumpers great, then all you need to do is transfer everything and maybe lengthen the cables. Here's the catch if you want to add lights and other sounds, you will have to either add more bumpers and switches and add electronics seperately for those, in which case the score won't be updated on those (if this thing has a scoring system). If it doesn't have a scoring system hey easy , but if it does you won't be able to add to the score with those other ones unless you dive deeply into electronics. Doable yes, fairly simple if there is no scoring system, if there is a scoring system you could trick it into believing that some other sensor had been triggered and make that switch on the additional bumper close another as well as trigger the other thing (out need a four contact switch to seperate the original circuit from the other one, but heck that part is easy. As for adding speakers, heck computer speakers are perfect, use the output from whatever the toys speaker is and hook it up to the computer speakers input, however if you want to keep it simple for you you need to seperate the toys, so if another one also has sound you might want to go with seperate channels. Just keep the circuits seperate, and if these things require different voltages you might need to add some simple voltage regulators. As for adding flashing lights hmmm depends, if you want those to be triggered by something you'll have to work off whatever that circuit puts out, so if it lights up a certain thing, you'll use that to drive a transistor as a switch to turn on whatever flashing light, because I doubt the board will output enough power to power additional lights etc. my .02 terramir PS: some pictures of the layout of the thing from inside and out and explanation of what each bumper outer trigger does now and a sketch of what you want to do and add and the layout of your new thing would be helpful. terramir
  6. What I need is a circuit That will transfrom my 17V DC into something with quite a bit of frequency, I know if it's a capacitor based solution I might end up with higher voltage spikes, but on the output end I can smooth things out with capacitors again :P so I can feed it through a transformer to be stepped down and current gained. Background on the idea is below. Short version DC through transformer efficently as possible to gain charging current. Terramir Background: I got solar panels, catch is they deliver around 17V and lets say at one given point in time 5A (can be anywhere from .1A to 6 eventually .1A to 9 When I put my third panel up. mmpt's are expensive and not that efficent when it comes to 12V systems. So I had an idea, instead of constantly measuring and losing alot to electronics inside an mppt, build a transformer based system. Well thinking to myself, Use a transformer which I rewind so it has a nice 17V input and the secondary windings have have several taps that of which only the voltage needed at the current moment get's switched on. Latching relays steered by a pic should do the trick, hey and that pic circuit will use virtually no power except for like the measuring, which won't cost much, the sleep inbetween, and the big real power usage (5V maybe 25 mA=.125W) will only happen when the logic decides it needs to switch relays, maybe once every two three hours lol for like a min maybe .02Wh a day. Catch is I need some way to convert my nice little dc looking like this: -------------------- into something that looks like this: v^v^v^v^v^v^v^v^v^v^v^v without losing any power (well sub 1% loss would be nice plus the loss I will get from the transformer (hoping to keep that low) and then after it's transformed and comes out I'm thinking of hanging some 1000 micro F capacitors to smooth the voltage back into a nice -solid line :D like this ----------------------------------- Heck I even have one 25V 4700 micro farad capacitor this way I could get more power out of my solar panels ironically the lower the batteries will be at the time the higher the gain will be, but even at a 17V to 14.5V ratio (when the batteries are pretty full) mathematically I could gain like 17% mathematically at a 12.5V output a 36% gain. But even a 15% overall gain after losses would be better than doing nothing. ;D terramir
  7. well I was actually hoping for a relay that has leads for each switch position (i mean trigger leads) but bi-stable relays could work too I'm gonna search online for some now :) thanks any more info would be appriciated terramir
  8. ??? My question to the community is the following is there such thing as a relay that will stay in either in switch 1 or switch position 2 without constant current needing to be applied to either one or two. I mean usually a relay stays in the switch one position and lets current through to one lead and when you then apply current it will switch to the other lead, or the relay will switch something off or on depending on where the lead is attached to. But usually in order to stay in the "B" position a constant current has to be applied to the relay. Are there relays that use the magnetic force for just a second to switch it to the b position and need current only to switch it back to the "A" position? this would help me in designing my alarm system.
  9. 1-5 will be on another pin because that voltage will be measured constantly while the individual cells will only be measured during charging, and only as a spot check during discharge. discharging monitoring the main 1-5 is far more important and the cells then are only checked at certain levels ergo the total voltage will give an indication, during charging exceeding 4.2 on a individual cell is dangerous, during discharge if the total pack drops below 13.6 volts then it's time to measure the individual cells more often ;) because no cell should drop below 2.8V it could harm them! before once every few program cycles is fine. the voltage divider is needed because most pic's can't exceed a 6V input it will be needed not for the individual cells but for the 1-5 bridge Li-ion's are tricky things I also have to measure the output and input current input to determine when it's getting full and for safety output because it should not exceed 3C the a disconnect is very necessary there will also be a 3.2C hardwire fuse. In case the chip fails. LI-ion's are easy to charge but if something goes wrong bang they vent with a flame. the open voltage should not exceed more that 1V above the packs capacity with mine 4.1V max cells that would be 17.4V that will be dragged down by the charging to 16.4 when the current proceeds to drop to 3% of C which in this case is 1050 mA ergo 31mA they are full at 70% of C the voltage should be 16.4 total 4.1 each but if there was an unequal charge that's where the trouble begins. if one cell is already full it will rise above the 4.1 V and start draining more current a disconnect is needed to prevent a flame burst(ergo explode). as for that switch you are talking about can you give me some more details? Thanks terramir
  10. First I need a voltage divider I know that is two resistors but I’m a little unclear on how that would be wired to an adc Second I need a circuit that can measure charging current based on an adc while it’s still isolated from the adc I can’t have the 1 amp going to the adc pin, but I can’t restrict the current flow to the charging cells. Third I need to learn how I could switch what is coming in to an adc pin so I can measure 4 independent voltages with one pin. What I mean is the following let me see if I can make a small schematic with my keyboard | + cell one - |+ cell two -|+ Cell three -|+ cell four -| | | | | | 1 2 3 4 5 well the thing it if I want to measure the individual cell voltages, how could I do that I mean they can’t have a common ground and still be wired in series for charging and output or can they? Anyone got a solution to this doozy because quite frankly I’m at my wit’s end with this one. I mean series and parallel at the same time anyway I see it just adds up to one giant short circuit to me :s the only way I could see doing it is probing one and two then 2 and 3 then 3 and 4 and the 4 and 5 in succession but the nightmare there is that I don’t have a common ground and I need to switch both the ground and the positive every probe time which means either micro relays which eat up lots of energy compared to transistor switches and add components I think A. I would need transistors driving the relays to amplify the switch current from the PIC port B pins. B. What I wanted to do is have two pins switch the adc cell probe pin like this. : both pin 1 and 2 high = cell one, pin 1 high and pin 2 low cell 2, pin 1 low and pin 2 high cell 3 and pin one and 2 low would equal cell four. But the more I think about that I see per switch state I would need either relay for both the positive and negative testing points or I would need to use both a pnp and an npn as switches this is turning out to be a nightmare anyone got a more elegant solution. I know I can use a transistor as a switch but this is also a problem since I need to switch both rails. Anyone got a solution for me here. terramir
  11. well I needed to build some li-ion chargers, I got the cells and well I got some surface mount Grrrr :'( darn chips (samples so no big loss), I looked at them and unless I spend like 150 bucks it's not realizable. for the adapter for the prototyping and then well afterwards to have then throw on a mask to make the pcb's, so I thought I go the more elegant route and start designing my own charger the cells as long as they get a stable input charge themselves the charger for Li-ion is just a security precaution. my cells are 4.1V max and I want to build 12 yeah 14.4 nominal 16.4V max I got 50 cells fairly cheap just 50 bucks and I think once I get the circuitry down pat it will be fairly easy to design and build the packs. But now I have to get away from plug and play electronics and program my own pics and stuff I started this as a solar project I built three panels And still have cells for two more. All of them are not being used right now 36 cell panels 18V open voltage up to 3 amp short circuit current. well I got more nimh and li-ion that I know what to do with it was a neat idea, but now the only problem I have is that with the different chemistries and about 10 AH worth of gel cells as well total about 35 Ah's to be upgraded as needed. the panels could produce much more but I live in an apartment and there not on the roof they are in my windows. got enough power as soon as I hang the three back up I don't have an intelligent system to switch the power from the solar panels depending on time of day well actually power output from the solar panels I want to design the system based on PIC's because: A: they are really cheap B: the are so versatile that I can do everything with like 20 chips that includes a central console that will tell be exactly how much power is in everything at the current moment. this way I won't be wasting power or cells because I can even inteligently discharge them using the more fragile gel cells only for heavy loads, discharging the li-ion's to 40% charge(40% is the value that keeps li-ion's alive forever otherwise they destroy themselves after three years) during low power (sun) phases and relying during those times on the nimh banks, which are the cheapest to replace and upgrade. this all can be done cheaply and reliably with PIC's but I hit snags at every turn, I want to use the li-ion cells for my model airplane and to power various other portable projects as well so I need those pic's more than anything else. I need to learn the basic circuits I need to design for the voltage and ammeters that I need the PICs to have with the built in D/A convertors, it is supposed to be fairly simple to make internal ammeters and voltage meters for the battery packs. while observing the Li-ion discharge curves I can even calculate what percentages are left in the cells I can even somehow design a subroutine (software-wise that will keep track of the battery useful capacity) the software stuff is all good I wrote the mock code already all I have to do is learn the actual syntax which is not a problem, my problem is to design the other basic circuits so I have voltage meters and two ammeters. and the switches to switch between four measuring points for one ammeter and one voltage meter. This is why I need to learn all this stuff from the ground up. plug and play won't do this time. I have all the data needed on my battery chemistries, Li-ion are the simple ones actually the PIC's just need to be in there for safety (LI-ION are easy as long as there not overcharged or short circuited and all cells have an equal charge) you short or overcharge those babies you can have quite a mess on your hands (talk about bang) :o please help terramir
  12. Hi guys I'm an advanced computer builder, but I got the small problem in electronics I'm a complete and utter novice, I want to learn how to program and design curcuits based on pic processors, but there are so many factors to consider, I really need some recomendations on how to learn this stuff from the ground up and fairly quickly, I know what a resistor is as well as some of the other basic componets (transistor, variable resistor capacitor etc.) but I need some links to websites that will give me all I really need to knowone step at a time I'm fairly smart and pic up on things fairly quickly. My biggest problem is that I have no money to spare at the current moment, except for a few bucks here and there so I am looking for web sites and stuff to really learn the basics to advanced stuff. terramir
  • Create New...