Jump to content
We’re excited to announce the forum is under new management! Details to follow.


  • Content Count

  • Joined

  • Last visited

About woolyhead

  • Rank
    Registered User

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. No, they are lookalikes but in the past they have worked ok
  2. Thanks swarfendor 437. I'll give it a go right now...... Well that didn't work for me. I keep getting the message "Cartridge error. Refer to documentation." But thanks for trying to help me.
  3. I put some new HP inks into my HP C5280 printer and it still refused to print. It gave the message "Cartridge error. Refer to documentation." I think this error message is false but the problem can be solved by resetting the printer. But how should I do this? I looked it up on the net and all I could find was a video with no sound and it was too difficult to follow. Could someone please help me.
  4. Thanks the bloke and medusa. I will take a better look at it.
  5. My electric oven has a fan inside and when cooking, hot air comes out into the room. Are fan ovens supposed to do that?
  6. Looking at many of the circuits shown on the net for giving constant currents, they mean by this term that the CIRCUIT APPLIES A VOLTAGE to the battery and whatever current tries to flow, the circuit limits it, even if the battery voltage drops. If the battery voltage rises the "constant" current no longer stays constant but reduces. That's all very well but the term constant current really means that THE CIRCUIT APPLIES A CONSTANT CURRENT to the battery and this is maintained constant whatever the battery voltage does/is. So whether the battery voltage rises or falls the current remains constant. with a proper constant current charger. There is a clear difference between these two types of charger. To monitor the negative dV/dT that occurs when the battery is fully charged the current source must be one of the latter kind, a genuine constant current type. Pulse charging is something else and I don't know much about it yet but I think it offers advantages over the dc type in that the battery responds better. I look forward to seeing any ideas you come up with. Since writing this I found the following comment on Battery University about pulse charging:- "Interspersing discharge pulses between charge pulses is known to improve charge acceptance of nickel-based batteries. Commonly referred to as a “burp” or “reverse load” charge, this method assists in the recombination of gases generated during charge. The result is a cooler and more effective charge than with conventional DC chargers. The method is also said to reduce the “memory” effect as the battery is being exercised with pulses. While pulse charging may be valuable for NiCad and NiMH batteries, this method does not apply to lead- and lithium-based systems as these batteries work best with a pure DC voltage."
  7. Thanks Ghozer. Your idea would produce a charge current of about 100 mA which is C/10 for a 1Ahr cell. This is a rather slow charge rate because NiCads can take a higher proportion of C and this makes the charging quicker and more efficient. Since I'm using D cells which have a C value of 4Ahrs I was really looking for a constant current charger giving about 2A and also a circuit for detecting the negative deltaV point. I looked up those references, apelike, but couldn't find either such circuit. Most of those shown were not proper constant current supplies. Ghozer's circuit is almost constant current, independent of the cell voltage, but I need 2A so if I increase the dc voltage to say 100V and use a 50 ohm resistor I should get 2A, But the wattage in the resistor would be 200W. That seems a bit extravagant in terms of power. If I reduce the voltage to 50V and use a 25 ohm resistor the wattage is then 100W. If I retain the 25V supply and use a 12.5 ohm resistor the wattage is still 50W. All these options seem like a hammer to crack a walnut. Since the cell voltage is only about 1.6V or so while on charge at most and only changes by about 0.6V from a starting voltage of say 1V, it shouldn't need a very big resistor value to make the current independent of cell voltage. Suppose I use 4V supply and a resistor of 1.35 ohms, the wattage would be about 5.4W. The current would be (4-1)/1.35 = 2.22A at the beginning , falling to (4-1.6)/1.35 = 1.78A. This is 2A plus or minus 10% at the expense of only 5.4W. in the resistor. What do you think of this scheme? Is the current constant enough for an NDV circuit to work? I think the NDV reduction in cell voltage is of the order of 8mV.
  8. I know this subject has been worked over many times before but I just took an interest in it and thought someone might be interested enough to answer my question. Here's my story so far:- I don't possess a constant current charger so I use a cheap commercial type. which is not very constant current. It isn't constant voltage either but is a voltage source in series with a resistor chosen to give charging currents of about C/10. It doesn't sense the reduced slope, the dV/dT that occurs when the cells are fully charged. I read in a survey of NiCad chargers that this reduction is very small and can't easily be seen unless the charge current is at least C/3. .The article also said that low cost commercial chargers use a thermal cut out and this is not very good design because by the time the cell gets hot enough to trigger it that's damaging for the cell. They also monitor the charge current and when it falls sufficiently they switch the charge to trickle charge. (This backs up my statement that it isn't a constant current charger). I monitored the individual voltage of every cell as it charged using my commercial charger and was quite surprised to see them go up to 1.4 and 1.5 and in one case 1.635 volts. I had thought they would all stop at 1.35 volts when almost fully charged but still on charge. The sum total voltage is 18.38, equal to the off load voltage from the charger thus proving that it isn't a constant current charger. My question is can anyone give me a circuit diagram for a constant current charger supplying 12 off D cells, all in series connection and requiring a constant charge current of C/3 so as to see the full charge dV/dT reduction when it occurs. I would also like to have a circuit for sensing this reduction in dV/dT if possible.
  9. Hi Onewheeldave. What I'm asking was contained in my post. Here it is again.....why does that make it unlikely that present day British captains of nuclear submarines would do the same thing?
  10. So, just because one, maybe two, Russian submarine captains (and maybe a rogue British sub officer - who knows?) refused to press the nuclear launch button, why does that make it unlikely that present day British captains of nuclear submarines would do the same thing? And since they are selected for the job they now do, what connection is there with young people in general (who haven't been selected or trained for launching British nuclear weapons)?
  11. I'm a qualified electrical engineer with many years experience. I've even worked on the design of alternator electronics for vehicles but I must confess I have no idea what this discussion is all about. If my car battery ever went flat I would connect a 12 volt battery charger to it and inject a few amps for an hour or so. The connection used big croc clips straight on to the battery terminals. What are these 3 pin adapters you are discussing? What do they adapt and to what and what is the adapted output applied to? Please explain. It's the 200mA bit that intrigues me. Surely that isn't the battery recharge current? Is it the mains current? 1 amp battery current at 12 volts corresponds to 50mA at 240 volts. That's 50 mA mains current per amp of recharge current. So are you working on having 4 amps battery recharge current? All these figs are approximations of course.
  12. Mr Fisk, now that you have clarified things for me by saying "there is NO difference between Muhammad and Jesus- both were messengers of God," I understand. I previously thought you were implying that Muhammed is somehow seen as the true messenger and Jesus a lesser one. Thank you for explaining this.
  13. Mr Fisk, you said Jesus is A messenger of God in Islam, son of Mary. Earlier you said that Muhammed is THE messenger of Allah. Why the subtle differences in your uses between A and THE?
  14. Sorry, I made an obvious mistake. What I meant was Why isn't Muhammed just one of the messengers and Jesus another?
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.