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  1. M

    Generating 24VAC Output (2 Amp Capability) from 36-40VDC

    Can I use an H-bridge chip to accomplish this? If I wanted to do a square wave to approximate a 24VAC output, would I use 34V and negative 34V? Or would I use 24V and negative 24V? These are the H-bridge chips I was looking at: DRV8251DDAR...
  2. M

    Generating 24VAC Output (2 Amp Capability) from 36-40VDC

    24VAC Valves only - no DC valves. On the more rare occurance it will power 24VAC relays, and control HVAC devices that require 24VAC signals to operate. Sure, some of the things "might" work with 24VDC. Technically they can put whatever they want on the power source, so long as it doesn't...
  3. M

    Generating 24VAC Output (2 Amp Capability) from 36-40VDC

    Solenoids are not the only thing that its going to power. 90% of the time it will be solenoids. It has to be 24VAC output. Yes it is a lot of effort but it has to be done, there is no way around this requirement.
  4. M

    Generating 24VAC Output (2 Amp Capability) from 36-40VDC

    I've already suggested this to everyone that this is simpler - everyone hates the look of a massive transformer and is absolutely not going to work for this. It has to be a 120V plug (C8 plug receptacle), and it has to be small.
  5. M

    Generating 24VAC Output (2 Amp Capability) from 36-40VDC

    24VAC transformers capable of 2 amp load (48VA) are massive and are not even close to the size this device needs to be.
  6. M

    Generating 24VAC Output (2 Amp Capability) from 36-40VDC

    There is a power module on the circuit board that receives 120VAC and converts it to 36VDC. You need 34VDC to create the peaks of 24VAC. I have to create a 24VAC output. DC output is not an option.
  7. M

    Generating 24VAC Output (2 Amp Capability) from 36-40VDC

    I want to use this to drive rainbird sprinkler valves. Ideally the output would be sinewave if I can pull that off - but technically they run ok with a 24VA squarewave as well. Either will work. I want to incorporate it into a PCB to just use raw components.
  8. M

    Generating 24VAC Output (2 Amp Capability) from 36-40VDC

    Hello, I am wanting to generate a 24VAC output, and be able to put up to a 2 amp load on it. The available power is 36VDC or 40VDC (3 or 4 amp). No transformer - this has to be generated off the main DC voltage. As we know, a 24VAC output consists of a sinewave with a peak voltage of +34VDC and...
  9. M

    Capacitance Measuring Circuit - Can This Circuit Be Changed For Higher Frequency?

    Thanks again for the response. That chart in my initial posting has the capacitance values involved. Completely dry reading is under 100pF. A little bit of water is around 11.5nF. Pretty wet is closer to 10uF, and fully saturated is around 15uF.
  10. M

    Capacitance Measuring Circuit - Can This Circuit Be Changed For Higher Frequency?

    Thanks again for the response! Resistance based sensors, or circuits that measure EC (electrical conductivity) is popular, but they are drastically effected by the salinity of the soil. The capacitance based method is supposed to be the more "accurate" way of measuring soil moisture as salinity...
  11. M

    Capacitance Measuring Circuit - Can This Circuit Be Changed For Higher Frequency?

    Thanks for the response! Are you suggesting doing something like this? I didn't put the LED's in the mix, because in the end I still need to read an analog value to determine the capacitance: e.g. run the analog value into an ADC and do a calculation. Thank you as well for the response! The...
  12. M

    Capacitance Measuring Circuit - Can This Circuit Be Changed For Higher Frequency?

    I came across this circuit that measures capacitance mainly between 30pF and 300pF, and is typically used between 31KHz and 250KHz. It basically outputs a 0-5V analog value that correlates with the capacitance. I drew a green arrow pointing to where the measurement is taking place. Its basically...
  13. M

    3 Phase Motor - 3 Individual Circuit Breakers - Detect if 1 Breaker Tripped And Shut Down Motor

    Hey guys, so I did get a chance to try this out. I ran each phase through a 51K resistor and through an opto-coupler (part # TLP290-4(GB-TP,E) ). The optocoupler, paired up with a capacitor and a pull down resistor generates a nice clean 0V for "phase disconnected" and a 3.15V for "phase...
  14. M

    3 Phase Motor - 3 Individual Circuit Breakers - Detect if 1 Breaker Tripped And Shut Down Motor

    Would it be best to use the opto IC's across the breaker, so if the breaker trips, the opto IC would start conducting. Or would it be better to use the opto on just one side of the breaker along with a neutral. This would start conducting immediately and would stop as soon as the breaker trips.
  15. M

    3 Phase Motor - 3 Individual Circuit Breakers - Detect if 1 Breaker Tripped And Shut Down Motor

    To answer some of the questions and to clarify - the main breaker box contains a proper 3-phase circuit breaker. Its my device that contains the relays and a much lower amperage circuit breaker for further protection. This part is mainly to protect the traces on the circuit board from excessive...
  16. M

    3 Phase Motor - 3 Individual Circuit Breakers - Detect if 1 Breaker Tripped And Shut Down Motor

    Hey guys, I am turning on and off a 3 phase motor using a triple pole relay. I am also using 3 individual circuit breakers (one for each phase). For this application, I can only use 3 individual circuit breakers/fuses, as opposed to a single circuit breaker that has 3 poles in it. I am wanting...
  17. M

    Resistor Pull-Up/Down Problems With Relay Driving Circuit And Darlington Transistor

    I have actually tried the 2n7002 as well, and this also works. This is not the problem though. The problem is with the power startup and the default pin state messing everything up. This is not an option unfortunately. Most relays need between 70mA and 200mA, that would be a specialized relay...
  18. M

    Resistor Pull-Up/Down Problems With Relay Driving Circuit And Darlington Transistor

    Hello, I created a relay driving circuit using an IO extender (PCF8574) and darlington transistors (MMBTA13). I was originally not aware that the IO extender can only source 100uA of current for an output... knowing that now I would probably design this quite differently. This is why I am...
  19. M

    Most inexpensive method for detecting if some current is flowing in 120VAC or 240VAC PCB Trace

    So it sounds like the only feasible option is to cut the trace, and insert in an ACS730? (this one being a 30 amp version). The reason why I was being cheap with it was because I didn't need all the features of the ACS730, so it seemed like surely there was a cheaper option with less features...
  20. M

    Most inexpensive method for detecting if some current is flowing in 120VAC or 240VAC PCB Trace

    I looked up the part on digikey and they are labeled as "Not for new designs", they also start at $5, and plateau around $2.50. Since this is something I plan on getting assembled it has to be a legit part that can be sourced.
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