smd veroboard
I'm in 4th year of electrical engineering (in French school so sorry for my bad English) and that's my first time on this forum. I'm what you could call an beginner with some knowledge!
Here is my problem. I'm searching for a power supply for a robot we are building in one of our course. I need it to be able to give 2.5A as Vout and 8.5 V (with really little tolerance on it because it gives power to a very old onboard computer). I plan to use batteries (8 or 10 AA for around 10 mins of autonomy at the lowest prize). I went to national.com at the power supply design too and got this schema (see attachment)
I must tell that I already got all components except the coil. So I don't want to redesign the whole circuit and buy again everything. I've got 2 problems:
1st: I don't know where to get coil of 8.86uH (0.17 ohms) (I live in Canada in Quebec city)
2st: The sample I've got from national semiconductors (I have purchased it on their website and I have received it yesterday from Singapore!) is a surface mount. It's 16 pins and very very small! I need to be able to put it on a veroboard. So I would like to find a way for that and also to know if the electromagnetic will cause a problem (the chip is made for running from 100kH to 500kH)
If someone could give me a hint or help, it would be very nice!
Thx
P.S. I'm not sure if in English you use Veroboard as an word, so I've joined an example for those who may not know what I mean...
One option is to gently mount this 16-pin SMD IC on top of a 16-pin DIL IC socket .. see attached picture ..
As far as the 8.8μH inductor is concerned, you can use part of an RF-antena rod from an old transistor radio, wound, say, 20 turns, and measure inductance ..
If you dont have an L-meter you can build small LC-oscillator with know C and calculate L from frequency of free-oscillations .. ω2=1/LC ..
Regards,
IanP
well thanks for your help. Where do I get this component ? It look like really hard to place de TSSOP on that DIP... don't you think there is easier solutions ?
If you look like again at the schema I've put on my post, you'll see there is already an second order LC low pass filter. I may change these values for using a coil I already own (2.39mH), but don't you think that will change impedance of the circuit in general and modify how the system works ?
I think they've used an Coil at low value to have the impedance at the lower possible value for not consumming power in the coil : jX=j2PifL. According to this simulation (see attached file), T=1.75us = 571kHz and that makes X=31 ohms ==* 0.25 A at 8.5V (out) = 2.27W lost in the coil... (mabye my logic is not good... I'm not quite sure of what i'm writing...)
Thx