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  1. CDRIVE

    Grounding and Circuit Noise

    Thanks Hop, but it's too heavy for my retired mind. I don't understand why this (same) topic was started. Chris
  2. CDRIVE

    Clap circuit for DC motor

    I skimmed through the datasheet specs. It says that it's TTL compatable, which doesn't necessarily translate to uC compatible but unless I missed something I'd have to say yes. That said check out Ebay to see if you can find an H-Bridge in module form. It will save you PCB work. Chris
  3. CDRIVE

    How to control the speed of a 24vdc pump from circulating water temperature?

    Good! Nothing changes... For now...;) Chris
  4. CDRIVE

    electrical task

    That's not a single wire. Chris
  5. CDRIVE

    electrical task

    We have a policy here at EP regarding class assignments... We don't do them. At times we'll offer suggestions to point you in the right direction. At best we may include block diagrams and or partial schematics but that it. Chris
  6. CDRIVE

    How to control the speed of a 24vdc pump from circulating water temperature?

    So you had to un-solder the male receptacle on the board to rotate it? Whatever you had to do is OK. I just needed confirmation that your measurements were made with Black = GND, which you said it did. Manpower is dirt cheap in China so it wouldn't surprise me if human hands inserted the...
  7. CDRIVE

    How to modify 12-24v car phone charger?

    This sounds like a syndrome of the digital age. When all we had was analog meters we could barely see the difference of a 10th of a volt with the exception of the lowest range. Chris
  8. CDRIVE

    Clap circuit for DC motor

    An Arduino will make your project easier but I would swap the transistors in the H-Bridge circuit. That circuit uses an Emitter Follower configuration. I would put the PNP's where the NPN's are and put the NPN's where the PNP's are. This way you can control it from the 5V output levels of your...
  9. CDRIVE

    Help with 555 timer circuit

    I forgot to mention that the speaker should be coupled to the 555 though an electrolytic cap. If it isn't it will respond to only half of a cycle. Chris Edit: This is poorly stated so I'd better correct it before I get a flogging. What meant to say is speaker (audio output) responds to a...
  10. CDRIVE

    Help with 555 timer circuit

    Just a thought but maybe his supply can't deliver 200mA or he's using a MOS 555? Chris
  11. CDRIVE

    Grounding and Circuit Noise

    I forgot to mention that Max specs means just that. It's never a good idea to operate any component at its maximum limits. ;) Chris
  12. CDRIVE

    Grounding and Circuit Noise

    Got that but I think a voltage regulator would be a better choice. When dealing with extraneous noise pickup it's hard to beat differential inputs with high common mode rejection. That's how EKG machines reject much higher ambient noise while still measuring our bodies (minuscule) impulse...
  13. CDRIVE

    electrical task

    I see the word "we" which appears to be homework. Regardless of that issue I think you need to explain in greater detail what your instructor wants from you. I can't help but think that it's not actual conductivity measurement (measured resistive value) but rather a 'Yes the liquid has reached a...
  14. CDRIVE

    Grounding and Circuit Noise

    I don't see anything odd about GND in your circuit but I must admit I'm lost with your + & - supply to OpAmp C. Unless OpAmp A is a separate chip from OpAmp C this can't be done because a single chip shares the same supply pins. On that note I've never seen an OpAmp circuit that divides the...
  15. CDRIVE

    RTL logic 0 and 5 V

    This circuit will keep your logic intact. If you want to make the output TTL compatible reduce R21 to about 1KΩ to 2KΩ. Chris
  16. CDRIVE

    RTL logic 0 and 5 V

    Harald, if he uses a single PNP won't his logic will be inverted? Chris
  17. CDRIVE

    How to control the speed of a 24vdc pump from circulating water temperature?

    Forgive me if I seem dense but are you saying that the receptacle is soldered to the board reversed? International color code acceptance: Red = Positive (+) Black = Negative (-) In order for the analog logic of my Thermistor circuit to be correct your color code must follow this. I also need...
  18. CDRIVE

    How to detect very high frequency sound ?

    Here's an ultrasonic detector that produces an audible alert. Chris
  19. CDRIVE

    How to control the speed of a 24vdc pump from circulating water temperature?

    Alec, that makes perfect sense. Now when I read head scratching, Chinese tech data I'll just be thankful that it's 'at least' read left to right! :p Chris
  20. CDRIVE

    How to control the speed of a 24vdc pump from circulating water temperature?

    Hi Alec. Hopefully Stu means as shown below. I'm surprised the plug was easily able to be inserted reversed. Stu, I'm almost certain that the heat sinked component on the right side of the photo is a 5V regulator. Your 6V battery supply is too low and why your not reading 5V with the Pot at...
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