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  1. OLIVE2222

    Replacing NiMh in phone

    Steve, You can probably use the existing charger as supply for the Lithium charger but Lithium batteries are far less forgiven than NiMH. They need a preconditioning phase, a current regulation phase and (a very precise) voltage regulation and charge termination phase, sometimes a safety timer...
  2. OLIVE2222

    Automatic battery charging circuit

    Hi, No the MAX1555 can handle a maximum of 280mA and max 500mA for the MCP73831. What are you batteries capacity (the mAh figure) and what charging time do you expect? Olivier
  3. OLIVE2222

    LM317 question

    Also the diode bridge output is reversed and D6, being shorted, is useless. Olivier
  4. OLIVE2222

    LM358 problem

    Ok I have the full picture now! You will learn a lot with your setup, a good hardware/firmware mix. Few decades ago my first led learning was done thanks to a radio shack "led value bag" and few led burning on a 9V battery :D
  5. OLIVE2222

    Automatic battery charging circuit

    Ok so if you need something in the few hundred mA range the MAX1555 or the MCP73831 will fit. For higher current it can become more tricky. Olivier
  6. OLIVE2222

    LM358 problem

    Nice that is working now! Despite I am not talking about the gain resistor you find out yourself that you need something in the K range for the difference amplifier . To build this difference amplifier you need VERY precise resistor or, again, you will have offset problem. By the way what is...
  7. OLIVE2222

    identify this resistor

    The 5th band can maybe denote a fuse type or flameproof resistor type. This can make sense according to the low ohmic value. Olivier
  8. OLIVE2222

    Automatic battery charging circuit

    If the needed charging current is in the few hundred mA range, indeed, Ebay is the way to go. Many of them use USB port as power source. If you want to charge few of them you can go for USB wall plug or a powered usb hub. For DIY one you can use the MAX1555 for example. Olivier
  9. OLIVE2222

    LM358 problem

    The op amp is working correctly but the measured value and the offset error become not distinguishable. If you use an higher resistance you still have the offset error but the result is workable 60mV(worstcase) on few volts (and you can cancel the offset in the firmware). They are better op amp...
  10. OLIVE2222

    Capacitor replacement advice

    On the schematic cold side I see 2X1000µF/25V caps and 2X1000µF/35V caps You can go for 4X the 35V (assuming they fit on the available room) not the other way around. Look VERY CAREFULLY at the capacitor polarity, when wrongly mounted they can explode ! Olivier
  11. OLIVE2222

    LM358 problem

    You don't need a dedicated shunt resistor! You can use the led current limitation resistor as a shunt. If the measured voltage is to high just split the limitation resistor in 2. for example with a bottom resistance of 100 ohms you will have 1,5 volts for 15mA led current, a pretty good value...
  12. OLIVE2222

    LM358 problem

    Hi Spencer and welcome to this forum ! Look at the LM358 input offest, you will find a 2mV figure to be multiplied by your 30X gain. Even with the input grounded you can have 60mV at the output! Low shunt value are often used when significant currents are present to avoid losses. Here you...
  13. OLIVE2222

    wave soldering at home

    Well, looks to works but you still have the solder contamination problem and the solder cost. Olivier
  14. OLIVE2222

    wave soldering at home

    Well even if possible not sure this is profitable. If you only have one time 1000 pins to solder it's a 30 minutes jobs. The problem with solder waves is the solder contamination, you need to send a sample of the solder to a lab on regular basis to check it. When contaminated you must discard...
  15. OLIVE2222

    LM7805 - Linear Voltage Regulator And DC-DC Converter Analysis

    The datasheet of JRC version of the 7805 contain an equivalent schematic of the device. This can be useful to understand how the work. http://semicon.njr.co.jp/eng/PDF/NJM7800_E.pdf Olivier
  16. OLIVE2222

    Power supply help

    Hi Adam, Does the transformer already in the machine have multiple primary tap too? For instance you maybe have to high output voltage because you supply it with 240 V Ac on a 220v Input. Also what are the secondary tabs voltages? Olivier
  17. OLIVE2222

    Making an FM Transmitter

    This is almost the same design, results will be so very close Olivier
  18. OLIVE2222

    Making an FM Transmitter

    Well this is a very basic circuit, for best stability use a NPO type capacitor for C4 and build the circuit above a ground plane are probably the only possible improvement. For better stability you need a crystal or a PLL. For longer range you can locate the transmitter in a higher position...
  19. OLIVE2222

    Making two first circuits

    Yes the manufacturer give you the flexibility For your example, and for any relay, you have 2 data set: -The coil data, here a small DC voltage needed to drive the coil =your " voltage I have to apply to activate or deactivate the second circuit" -The contact data ,an higher AC/DC...
  20. OLIVE2222

    Making two first circuits

    Hi Alaios and welcome to this forum ! -For the relay you need one with a 3Volts DC coil Here a Farnell filtered result accordingly...
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