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  • Users: schnell
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  1. schnell

    Detecting ice in water pipes....by using a motor?

    Thankyou jraef, I am going to look for one of those flowmeters and check out the price etc. ...i just need to know "flow or no-flow" so i'm hoping i can get a cheap one...and preferably one with small paddles. Of course, as you rightly say, "Electric Showers" with 10KW heaters are used in...
  2. schnell

    Need solenoid valve which won't open when ice in pipe.

    Hello, Is it possible to get a solenoid valve which won't open if the water pipe is iced up? -but will open if its not? We design domestic showers which are tmperature controlled by stepper valves. If its cold and the cold pipe ices up , then only hot can get through and the customer gets...
  3. schnell

    Sending signal by voltage...or by current?

    Hello, The basis of this thread is: If you have a signal that you are sending across a PCB to a uC…..is it better to send the signal as a current , or as a voltage? (incidentally, the PCB has three ~5W SMPS’s on it.) - - - - ---- - - - - - - --- - - - - - - - - - - - - -- -- - - - ….is it...
  4. schnell

    Detecting ice in water pipes....by using a motor?

    skogsgurra, ....your idea is along the lines i should have been looking for in the first place....much better than a motor....in fact, as you no doubt are aware.....your idea basically describes a solenoid. In fact, on that point, we were considering adding some power-fail normally-closed...
  5. schnell

    Detecting ice in water pipes....by using a motor?

    edison123 Thankyou........... -with our showers, if the customer switches it on...it won't actually come on in the first place if the thermistor reports a temperature of zero degrees Centigrade. -This also applies to our bath fillers too. so hopefully our customer won't have started to...
  6. schnell

    Detecting ice in water pipes....by using a motor?

    btrueblood: steppers are commanded by a microcontroller. -the uC reads thermistor temperature of a thermistor in the mixed pipe, just after the stepper valves. ....you're right we can't risk too-hot water getting up to the shower-head as scalding is then a risk. badservo: Unfortunatley, we...
  7. schnell

    Detecting ice in water pipes....by using a motor?

    Hi, the shower unit is placed in the attic...which is very cold in winter in many parts of USA and uk. sorry it isn't so much the steppers breaking, as the cold water is frozen solid, and so the hot can come through alone and scald the person becasue theres no cold water mix.
  8. schnell

    Detecting ice in water pipes....by using a motor?

    Hello, We design domestic water temperature controlled showers. Stepper motors adjust hot and cold flow rates. If the water in the pipes is ice, and we try and rotate the stepper valves, these valves break. So do you know how we can detect if the water is ice or liquid.? ...its not...
  9. schnell

    Noise from NTC connection (temperature measurement)

    DPolak: Thankyou...i have in fact now suggested that we change to using an instrumentation amplifier. However, my boss and colleagues feel that i am being silly. They point out that the schematic that we have above (first post) works absolutely fine. Also, this application note from Texas...
  10. schnell

    Supply current of stepper driver IC when powered but not switching?

    Hi, Do you know what is the non-switching supply current (ICC) of the NJM2673 bipolar, switch-mode, stepper motor driver IC ?. NJM2673 DATASHEET: http://semicon.njr.co.jp/njr/hp/productDetail.do?_isTopPage=false&_productId=1690&_moveKbn=PRODUCT_DETAIL_MOVE_SPEC ...or download NJM2673...
  11. schnell

    Discrete FET driver turns off slowly.

    the thing is, with TTL totem pole, there is more shoot-through current, as you suggested....also, its three BJT's instead of two. If you mean "phasing" the switching of the two TTL totem pole transistors with two microcontroller pins....then that is out of favour for us, because we don't have...
  12. schnell

    Discrete FET driver turns off slowly.

    Hi, I have come up with two cheap FET gate driver circuits for driving the gate of a power mosfet in a switch mode solenoid driver. The PWM signal is provided by the output pin of a microcontroller. The solenoid current is 200mA. The FET Vgs(th) should be between 0.8V and 3.5V...
  13. schnell

    Flyback: a varistor between EARTH and the secondary's GROUND

    The ZDV must be to stop the secondary ground from floating up to high potentials with respect to earth ground. What you have found is either an industrial secret, as its not common, .............or a mistake by the designer
  14. schnell

    Flyback: a varistor between EARTH and the secondary's GROUND

    The ZDV must be to stop the secondary ground from floating up to high potentials with respect to earth ground. What you have found is either an industrial secret, as its not common, .............or a mistake
  15. schnell

    Damage microcontroller by driving FET directly?

    i am also noticing that 4 cheap, small FETS (IRLML2060) and two dual FET driver IC's (Clare IXDN602SIA) COSTS $1.36............... ..whereas.... ..four of the FETs that we are currently using (STB16NF06LT4 by st.com) costs $1.54 So driving the FETs directly from ther microcontroller is...
  16. schnell

    Damage microcontroller by driving FET directly?

    hi, basically , i believe that we should stay under the datasheet (page 304) "instantaneous" maximum pin current value of 25mA........at all times...even for small instants. -as is suggested, we could just put in a series resistor and get a slower transiton time....because the FETs we are...
  17. schnell

    Damage microcontroller by driving FET directly?

    I think the problem with just adding a gate resistor is that the internal resistance of the microcontroller pin has a wide tolerance band, ...from page 310 of the datasheet (graph above enclosed) you can see that the output resistance of the uC's output pin is anywhere between 83R and...
  18. schnell

    Damage microcontroller by driving FET directly?

    hi, The actual overall product which contains these four solenoids costs $1100. It is a "high quality" product at the luxury end of the market......generally customers are at least reasonably wealthy -Given this fact, is it then still the general concensus that all that is needed is a series...
  19. schnell

    Damage microcontroller by driving FET directly?

    The thing is, My boss does not want to add a gate driver, or series resistors, because he believes its needless overdesign. -also, adding gate resistors alone will simply slow up the switching on of the FETs, and increase switching loss. He points out that the FET's C(gs) is only around 316pF...
  20. schnell

    Damage microcontroller by driving FET directly?

    Hello, Will we damage our Freescale MC9S08AC60CFGE microcontroller by driving a FET directly from a microcontroller output pin, with no series resistor, (and no gate driver circuitry)? We are powering solenoids via switch-mode solenoid drivers which comprise FETs being driven directly from...

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