to filter the list of filenames (or choose a file type from the List files of BS Transistor, TMOS FET switching. Motorola. Q1, Q2. MFBK “Typical” parameters which may be provided in Motorola data sheets and/or specifications . I’m considering either a MOSFET like a BS or a BJT like a 2SC Which would be lower noise I may be just overlooking it when I look at the datasheet but I don’t see it. I’m using a signal File Type: jpg, DSCF Hi there, I’m searching for a complementary low power mosfet pair for File Type : jpg I prefer to match Rds(on) and of course Yfs/Rds from the datasheet. #2 is BS and BS which has comparable small capacitance.

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Hi Garbz, On my scope, a 10″ LXGPS, I have the dew heater just behind the corrector filftype which appears to be the best location, and the idea is that the heat going into the tube and slightly heating the back of the corrector plate, airstops the dew from forming on the front.

I’ve read also about too much heat as well might not be the best. As all scopes and setups and weather are different so lots of tweaking for optimal results. There it stays until conditions change. Might be power savings as well in light dew.

2n datasheet & applicatoin notes – Datasheet Archive

Each channel is unique, as for my setup I have a guide scope as well, so tweaking can be done seperately on each channel. The idea of putting the temp sensors under the dew straps, I picked up from lots of searches in astro sites looking for commons in temp sensor positions and under the dew heater seems datasbeet be the most intelligent things I read.

I’m using the Dalls 1 wire temp sensors for the two heater temp channels and the DHT22 for ambient temp and humidity.

The humidity sensor is on the inside lid of the small box that sits on the tube, and has holes in the lid to pick up the dew. Very nice project Chris. A bit beyond my skills. Shall follow with interest. Gday Chris I did something like this many years ago, and you will find it gets too complicated too quick, and too many cables go to one spot.

Have attached piccies of a unit i made up for fun that could a Have one DewHeater channel controlled via several means including using dewpoint, defined PWM duty cycle or auto temp delta mode. It doesnt come on till you get within a set delta from the dewpoint.

I also use dallas 1 wire temp probes and the system works quite well with much lower current draw than exposed units. Originally Posted by redbeard. Originally Posted by AndrewJ. As per redbeard, i also put my primary dew heater wires behind the corrector, but my insulated dewshield also goes right back over the OTA as far as possible to retain as much dewheater heat as possible in the OTA.

A double is still a float, just a double precision float is 64bits long instead of 32bits. Any floating point operation is very expensive on an Arduino or AVR as they don’t have a floating point arithmetic unit unlike say the CPU in your computer. Simply adding 2 doubles takes around instructions.


The fact you find a double works where a float doesn’t may point to a compiler issue. For efficient code you want to as avoid using any floats single or double which means no decimal places and avoid performing any math which results in a division that has a decimal place. What “noise” are you talking about?

You talking about ringing from the FET overshooting? You talking about actual radio noise being emitted every time the FET switches? The longer the FET takes to switch from off to saturated the more power is lost.

This can be achieved by either reducing filtype switching frequency MOSFET power-loss becomes a big issue at high frequencieshs170 by increasing the rise time of the MOSFET gate using a fast push-pull driver at the output of the microcontroller. Originally Posted by Garbz. Overshoot and ringing are a side effect of a crazy fast switching response which is usually the result of wanting to waste as little power as possible in the MOSFET.

To get that fileype of noise you need some kind of reactance capacitance or inductance either from components, cables, or even the MOSFET itself. A correct snubber can help. An incorrect snubber will simply make it worse. How fast are you switching? Are we talking Hz or kHz? The other way around the issue is to slow everything down if the application permits. This may eliminate the ringing even without a snubber. Exactly what I learnt in filety;e last lesson in Micros lecture only last week.

I was amazed the amount of code required to do floating point calculation compared to integer based calculation. One disadvantage I found which will have an affect more on Arduino platforms is the integer based calculation quickly use up 8, 16 and 32 bit integers.

So the best platforms are high speed 32 bit processors now. Freescale have a function called umuldiv that is specifically catered for integer based floating point calculations and just places two integers and a scaling factor. Some of the development boards I have a super powerful and nice to program plus unusually cheaper than Arduino. I am sure there are plenty of development platforms out there that are just as good though, but i have too many including Beaglebone Black and other smaller stuff.

I am not really interested be170 the Beaglbone though. Another really really cool platform is the PSoc4 platform which as a brilliant IDE that is component based and I believe super easy to develop. I will consider this as a possible option after completing this semester. Find all posts by mswhin Two choices of write frequency with the Teensy 2. I prefer Teensy boards using Teensyduino.

I figure this will permit a wide range of customisation. I don’t want to hijack your thread – strictly amateur stuff. Originally Posted by mswhin Originally Posted by rcheshire. Cheers Garbz for the heads up on the dew point calc. Your posts are an education. Last edited by rcheshire; at The freetronics smd mosfet runs a little warmer than the IRF I have, although freetronics advertise it as logic level Vgs 4. That is good stuff.



I understand datashete issue more clearly, for sure. Shouldn’t be too difficult to fit a gate driver circuit catasheet the box. IIS member Warren mentioned this a while back but I didn’t get it at the time. I need to get to the bottom of pwm frequency – resolution seems fef explanatory. I estimate it takes several seconds to indicate an increase in temperature of the cold finger.

I am guessing that 60hz is adequate, perhaps less. The strategy is to estimate the pwm value linearly for setpoint temperature and dither either side to maintain temperature. Changes in ambient air temperature are used to recalibrate pwm values – avoiding high, low switching.

Huh why can’t I edit my original post I was hoping to use it to update progress.

BS170 MOSFET. Datasheet pdf. Equivalent

Oh well I guess not. So far we are moving well. Ffet still need to test the prox switches, dew controller, and relay drivers.

If the devices don’t report in several times a second they drop off and may be forced to reconnect. This may not work. I’ve no experience with how much overhead a USB library takes but I guess we’ll find out soon enough. Also I’ve decided filetye drive the relays via an I2C port expander. Hi Chris, most excellent work Touch this against any part of the mount earth then there is a short cct to earth. Although I have seen some of these covered with heatshrink. I have tried them If a dew strap is using more than 3A Sorry for xatasheet long read I was working under the assumption of plastic RCA connectors and recessing the RCA plugs so frt they’ve mated there wouldn’t be any metal exposed.

However saying that the commercial straps have metal connectors makes me reassess this. Power dissipation is critical as I was targeting a SOT package.

I’ll reassess and see if I can switch the highside like get suggest with a suitably small package. Actually that’s not quite true, the advantages of lowside vs highside switching were mostly eliminated when I added the driver IC. Should be trivial filetypw change: Last edited by Garbz; at Yeah low on Rds is vital this is why most people use N channel fets Specifically as these have the Ishutdown sense.

Since on rds is a function of current passed but I found 12V 4A absolutely no problem dataheet the IR, doesn’t get warm at all. While these are low on rds there are no small packages for this family. You might get some P channel low on rds capable for the current drain in the SO8 packages though, but you lose the intelligent fet I shutdown, all depends on what you want. Of course this is a worst case fix and datasheey not generally necessary, but, some users do use RCA extensions or metal shield connectors, they will find out the hard way.

Also some plastic RCA connectors have exposed parts of the shield. Last edited by wasyoungonce; at It looks good but it’s not available from my usual sources for components either.