PICmicro circuits

  Microcontroller, JFET form low-cost, two-digit millivoltmeter ( This article has been accepted and published in June 22nd, 2006 ) https://www.edn.com/microcontroller-jfet-form-low-cost-two-digit-millivoltmeter/ Noureddine BENABADJI benanour2000@yahoo.com L.A.A.R. Laboratory, Department of Physics , University of Sciences and Technology - Oran , B.P. 1505 , El M’nouar, ORAN, ALGERIA , Fax : (213) 041.42.15.81 , Telex :22 701                The circuit in  Figure 1  offers an inexpensive alternative to commercial digital voltmeters. Although it has only two digits, it provides considerable flexibility and thus lends itself to customization by means of a microcontroller and its software. As one of Microchip's least expensive offerings, the PIC16F84A lacks an internal ADC. However, you can use a classic RC time-delay circuit to implement an analog-to-digital conversion by connecting capacitor C3 between lines RB7 (output) and RA4 (input) and in series with an equivalent

NoureddineBENABADJI L.A.A.R. Laboratory ( DTL team 2 ), Faculty of Physics,  University of Sciences and Technology - Oran, B.P. 1505, El M’nouar, ORAN, ALGERIA,    phone: (213) 041.42.15.81 The following circuit ( Figure 1 ) shows a home made non conventional galvanometer I designed a while ago to sense slow variable physical parameters, like temperature, humidity, atmospheric pressure, etc..., as I was definitively fed up after looking for a big analog galvanometer in local stores (not available, or very expensive…). I have build this prototype to add robustness (classic galvanometer are not suitable for harsh environments) and modularity for maintenance purpose (if the internal coil of a classic galvanometer is damaged, you have to throw it). Small servomotors are used for precision positioning , generally in robotics. They are driven with pulses of 1ms to 2 ms duration (critical), over a period of 20 ms (not critical). The maximum angle is 90° for the low cost model

NoureddineBENABADJI L.A.A.R. Laboratory ( DTL team 2 ), Faculty of Physics,  University of Sciences and Technology - Oran, B.P. 1505, El M’nouar, ORAN, ALGERIA,   phone: (213) 041.42.15.81 Briefly, in order to drive a multiplexed four 7-segment digits display, we need 7 + 4 = 11 lines (asuming the decimal point is not used) as shown in figure 1 . The references [1] [2] [3] may be useful to be read for full and detailed explanations. Previous EDN design ideas [4] [5] [6] show solutions to minimize the number of lines, to be able to use pin-limited microcontrollers. But those solutions require, in general, one (or more) additionnal digital integrated circuit(s), which increase components count, PCB footprint and cost. This article shows a solution to reduce the number of 11 lines downto 8 lines only, keeping the same number of components count . Figure 2 shows that mixing common-anode and common-cathode type, with PNP and NPN bipolar transistors require 7 + 2 = 9 lines on