4 Wire 3 digit LED Ammeter

A 4 wire 3 LED digit ammeter available from ebay in various current ranges (I favor the 0 to 999 ma ones) and colors (red, green, orange and blue). There may be more than one variety of mounting ears, but this part matches the ones I have. It is worth noting that the input wire for measurement is common with the negative power lead for powering the device, so if you want to measure current on the high side (i.e. the 3.3 or 5V power lines) you need to power the meter from an isolating dc-dc converter such as the Valor PM6078-004 (available as a Fritzing part). These ones don’t come with bezels, but bezels are currently available on Ebay. The 999 ma range are getting harder to find as stock runs down, so you may want to hurry.

Views created: breadboard / schematic / pcb

Views tested: breadboard / schematic / pcb

In the form of drag the part in along with 4 1 pin connectors, and connect a connector to each of the 4 active pins. Make sure the part aligns correctly on the grid and the connections all work in all views and the connector numbers match to the same pins in all 3 views. Have not yet used it to produce a board though. The two ground connections (meter power and Input) are bussed together in the part (and shown as an internal wire in schematic view) as they are in real life. This some times causes oddness in the pcb rats nest routes. As well the current input wires are off set by .05 inches from the .1 grid and Fritzing sometimes aligns to that rather than the power wires (which are on the .1 grid). I find turning off snap to grid and moving the part so the power pins are on the grid then re enabling snap to grid works.

(edit: updated this part to correct errors in PCB section)

Ammeter_4wire_led_1.fzpz (12.0 KB)

Peter Van Epp

1 Like