Is that the SOIC outline (pins 1/20 inch spacing)?i have already got the 2 IC's (4093,4013) in surface mount version
Which parts? What are their dimensions?I also cant go completely surface mount as a lot of parts are already in a box ready to be used
It wasn't clear at the time whether the terminals were those of the meter movement itself (coil), or of the input to the circuit; so I left them for you to connect. I've now connected them.you still havent connected the input part of the circuit to the actual terminals
Looks fine.will this thermistor be ok
I was trying to make the board versatile to allow options; hence places for the regulator and thermistor. However, I've been doing a bit more simulating and with the 4013 used, as you wanted, a 5V supply won't quite allow the 4093 to drive enough meter current for full-scale deflection. Even without the 4013 it's marginal.Also you said if it had the thermistor on the board you would eliminate the regulator , i see both are on this board. Is this because the board is using both 4093 and 4013?
R1 is the only component which generates any significant heat. Come to think of it, it could probably be replaced by an X2 rated capacitor to eliminate the heat source. I'll play with LTSpice, see what's possible, and get back to you.to avoid each component warming the next
I'm still at the learning stage with it!that eagle software looks good i must try to get used to it
Yes. If you right click on anything and select 'Properties' you get a dialog box where you can specify the layer the object (track etc) is in.Where you have red for top track and blue for bottom can i swap it around
Good idea.As chips are surface mount they can be soldered as SM then put a via next to each leg
That will work. Bridging of pins is hard to avoid usually; for once it will be useful.blobs of solder across pins
Ah. An unfortunate consequence of starting this design after the project was overdue for deliverycomponents were ordered today
It's still thereplease tell me you havent removed the thermistor
Farnell have them listed at £0.30 each.how much are these capacitors?
Not really, unless you want to optimise the temp compensation.thermistor is still on board it wont matter what temp unit is calibrated at will it?
Ok, but be prepared to swp 8k2 for a slightly different value. That's the value the simulation gives, assuming the thermistor is exactly 3k and has a standard temperature coefficient (beta) and the zener voltage is exactly 8.2V. A trimmer would have allowed better for component tolerances.do you think can i remove Vr3 and put back the 8k2 0.5W resistor ?
Don't know. The voltage rating isn't shown; and that's critical. It must be a good bit above the 200V RMS (I've assumed all along that 200V means 200V RMS ?) 280V peak.WILL THIS ONE WORK:-
Yes.those ceramic 39nf i showed you are they still suitable.
Sorry. Missed that.it is shown, they are 275v
Fine.i was going to use the 10v zeners
Yes. Initially set Vr3 at 8k2 then adjust Vr1 for 0% reading at 400Hz. Then set Vr2 for 100% at 440Hz. If Vr3 is too high the meter reading will increase with temperature (under-compensation); if too low then the reading will decrease as temperature rises (over-compensation).Can i calibrate this instrument using Vr1 and Vr2 and just use Vr3 at the end just to fine tune it.
Yes. Brain not in gear again. I assume movement is 2k, FSD is 100uA, and the scale reads 360Hz with 0uA (=0%), 440Hz with 100uA (=100%). If the movement isn't exactly 2k/100uA then the Vr2 adjustment should compensate for that.dont you mean adjust Vr1 for 0% at 360Hz,or 360hz on the existing dial
Yes.i have to set readings at 360 then 440 then put a case on and leave it running for a few mins
I don't think so. One or two twiddles of Vr3, at 5 min intervals as you suggest, hopefully will suffice.i could be there all day trying to get it right
Well simulation shows it should be more stable. But simulation is just that. The real world can be different. It's a chance that has to be taken as I'm not in a position to actually build this circuit so can't offer any guarantee on its workability. All I can say is that other circuits designed using LTSpice have performed in practice very closely to their simulation.as far as i will be concerned it will be just as unstable as previous version
When you power it up it should give a steady reading within a fraction of a second. Until you've got Vr3 adjusted correctly the reading will then drift slowly (hopefully only slightlyIf its left unchecked for ,lets say 30 mins when i reconnect it will i have to wait a couple of mins for reading to rise or fall to its correct position on dial or will it read correctly within a few seconds and stay on the reading?
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