Out for Fab!
I finally had to courage to commit to sending my prototype Lego train control module (LDCC + PF) out for PCB fabrication.
By any measure, this is a very dense circuit layout using very tiny surface mount packages. It bears keeping in mind that this module only measures 56 x 32 mm, i.e. 7 x 4 studs, and is less than a plate tall. A lot of the board area is taken up by the two strips of stud clearance holes to assist with mounting the module within a brick structure. I've kept these two strips clear of components to avoid interference. The PCB is double sided FR-4 and I'm hoping the generous copper poured planes will provide the bulk of the thermal heat sinking when in operation. The circuit should operate relatively "cool" due to efficiencies in design--the one area I worry about is the battery charging circuit when supplying the 10V / 500 mA charging current to the Lego LiPo battery. Depending on the power source, the charging circuit could dissipate up to 1.5 W--we shall see what happens in reality.
I've made a good start on the firmware, but there are so many details in processing the DCC protocol (I haven't even started the Power Functions protocol!) I hope all the code fits in the PIC 18F13K22 micro controller that I chose for the design!
I guess the next step is visiting the DigiKey website for the components--I'm hoping the part cost should be <$20--I haven't put anything exotic into this design--although I'll likely be forced into minimum buy quantities for some items. Ah well, its nice to have extra inventory. :)
Out for Fab!
I finally had to courage to commit to sending my prototype Lego train control module (LDCC + PF) out for PCB fabrication.
By any measure, this is a very dense circuit layout using very tiny surface mount packages. It bears keeping in mind that this module only measures 56 x 32 mm, i.e. 7 x 4 studs, and is less than a plate tall. A lot of the board area is taken up by the two strips of stud clearance holes to assist with mounting the module within a brick structure. I've kept these two strips clear of components to avoid interference. The PCB is double sided FR-4 and I'm hoping the generous copper poured planes will provide the bulk of the thermal heat sinking when in operation. The circuit should operate relatively "cool" due to efficiencies in design--the one area I worry about is the battery charging circuit when supplying the 10V / 500 mA charging current to the Lego LiPo battery. Depending on the power source, the charging circuit could dissipate up to 1.5 W--we shall see what happens in reality.
I've made a good start on the firmware, but there are so many details in processing the DCC protocol (I haven't even started the Power Functions protocol!) I hope all the code fits in the PIC 18F13K22 micro controller that I chose for the design!
I guess the next step is visiting the DigiKey website for the components--I'm hoping the part cost should be <$20--I haven't put anything exotic into this design--although I'll likely be forced into minimum buy quantities for some items. Ah well, its nice to have extra inventory. :)