Vacuum pen for pick 'n place

vacuum pen apparatus

pen and an assortment of nozzles

As I get older my hand is becoming too unsteady for using tweezers to pick and place certain types of surface mount components onto a pcb ready for reflow-soldering. I wanted to see if a vacuum pen would help.
I converted a really cheap aquarium compressor pump to work as a vacuum pump, by reversing the valve action. The 'pen' is a 5ml syringe; plunger not required. The 4mm bore tube for the air-line was passed through two rubber grommets and forced into the syringe. Hot-melt glue was applied inside the barrel of the syringe at the entry point of the tube to form another seal and reduce pipe movement. A small hole drilled into the syringe near the nozzle end makes a simple finger operated vacuum switch.

T-piece vacuum switch

For even better precision and control I subsequently fitted a T-piece for the vacuum switch, close to the pump, to be operated by my other hand. And I made another pen; of course with no hole. 

Half-wave filter for the MF amplifier

Two T200-26 iron powder toroids are used

It's called a half-wave filter because it functions like a half-wavelength of transmission line, ( e.g., coax cable ), regarding the terminating impedances at the design frequency of 475.5KHz. Using lumped circuit elements is a much more practical proposition than 200m of cable. It also has a low-pass frequency response; theoretically 2nd harmonic 951KHz -27dB, and 3rd harmonic 1426.5KHz -47.8dB. This is a useful amount of extra attenuation. So I built it for use with my MF amplifier, ( posted 6 December 2015 ), to provide additional suppression of harmonics in the transmitted signal. It is connected externally in-line with the amplifier output.