Verify a MOD4 FM transmitter schematic made in Eagle

hii i am new to eagle..I got fm tx mod4 schematic from audio guru i myself made the PCB design in the eagle application can any one please verify it once please before i am gonna etch it and try...i have uploaded the .brd and as well as the schematic with this post thanks in advance....

FM transmitter

I don't think you have got the hang of Eagle. Normally you would create a schematic. Then from that, you would create the board which would create a PCB with all the components and the interconnects shown as "rats nest". Then you would add the traces to wire it up.

Anyway, ignoring the normal work flow, some general comments:

1. you cannot get the board made by a PCB company - there are too many errors. In particular you have put vias under component legs. Move E$2 for example and you will see a via under one of the legs.

2. there is no board outline. Not critical for you to make yourself, but it is normal to define the extents of the board.

3. the board is a lot bigger than it needs to be, and given this is an FM transmitter (I don't know the frequency) I would make it considerably smaller.

Keith.

Re: FM transmitter

hii keith1200rs ok i ll fix it but can u please tell about that variable capacitor placement is it right or wrong??? and also what about the dc jack??

FM transmitter

I will have a look when I am back in my office but that may not be until Monday.

Keith

Re: FM transmitter

I designed my Mod4 FM transmitter (88MHz to 108MHz) and built it on Veroboard (stripboard).

The circuit board was designed to be compact so it is 2.0" long by 1.3" wide. it has spaces for two mounting screws.

FM transmitter

That's a nice, tidy stripboard.

Keith

Re: FM transmitter

sanjubluerock3 said:

hii keith1200rs ok i ll fix it but can u please tell about that variable capacitor placement is it right or wrong??? and also what about the dc jack??

Click to expand...

I cannot tell if the DC jack is correct or not without knowing a part number. It doesn't look right. I think the far right connection on your PCB is most likely the "ring" connection labelled 1 in the circuit. Be careful with the power supply - the connection on the circuit is drawn as centre negative - most power supplies use centre positive.

The same comment applies to the variable capacitors - without the part number of the device I cannot say what the connections should be. However, my guess is that the connections are wrong. I think the two connections opposite one another are likely to be shorted and the one at the side it is the variable connection.

It is often a good idea to buy the parts so you can check before you make the PCB if you are unsure about connections. It also allows you to check that your parts are the right size. Simple print the layout onto paper and lay the components on it to check.

Keith.

Added after 1 hours 14 minutes:

By the way, if you drew the schematic in Eagle first then when you create the PCB the connections will be correct. So, looking at the DC jack connections for the library you used, pin 1 is the "ring" which is actually the leftmost pin, not the right, as I thought.

The trimmer is not quite so easy because the library you used is incomplete. There is one symbol and several footprints, but only one footprint is associated with the symbol.

Keith.

Re: FM transmitter

thnks for your help keith1200rs so according to the schematic i should use the trm capacitor with 2 pins right???

FM transmitter

No, a trimmer with 3 pins is fine - it is just that two of the pins on a 3 pin trimcap will be shorted and you need to know which two!

Look in the "RCL" library instead of c-trimm. There are some trim caps in there, some of which are 3 pin. A lot of through hole ones are 3 pin. Very small surface mount ones tend to be 2 pin.

Keith.

FM transmitter

sir really i am confused here can u please edit and send me back so that i will learn by seeing it...

Added after 3 minutes:

rest all the connections are ok ??

FM transmitter

I will see if I get time later today. By the way, you have a few short circuits around the power connector - you have put all the tracks on one side of the PCB and they cross over one another.

Keith.

Re: FM transmitter

Thanks sir i will be waiting for your reply

Re: FM transmitter

I have fixed the short circuits round the power connector and the connections there. I have swapped one of the trim caps for one out of the RCL library. You need to do the same with the other trim cap.

I would really advise you to go through the tutorials and learn how to start with a schematic and generate the PCB layout from that. The DRC & ERC will then help to ensure that there are no connection problems.

Keith.

Re: FM transmitter

THANKS A LOT SIR.......

Added after 9 minutes:

from today i will first draw the schematic and then board.... thanks a lot