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ttl output from pc
Brian,
PICAXE18 is just a plain Microchip PIC16F88 and uses standard I/O pins for a software-only UART so that simple circuit is based on the input diodes of the CMOS port to protect against the negative voltage of the RS232 standard. The resistors in series with the pins are...
connect serial port ttl to pc
It's possible (and quite simple) to interface a microcontroller (like a PIC or an Atmel) to a real standard RS232 port like a COM on a desktop PC (some notebooks don't have real standard RS232 ports) using very few passive components.
The following schematic is...
Re: 555 replacement?
There are many 8-pin PICs with ADC like 10F222 or 12F675.
But there are many others with a comparator inside so with an external potentiometer and capacitor it's possible to have a "variable input" to set the delay.
With a 4MHz clock, you can get delay of hours or even...
555 replacement? a PIC
Why not use an 8 pin PIC like PIC10F200 or PIC12F509 ?
They have an 8 pin package like a 555 but have an internat 4MHz oscillator so they really don't need any external components (apart from the usual 100nF supply bypass capacitor) and can easily generate different...
From your schematic, it seems that R1 and R6 are in series with the GND pin of the MAX485. If this is true, it's wrong because in this way the resistor interferes with the power supply of the IC. Usually in RS422/RS485 connections, you don't put resistors on GND but simply connect the GND of the...
Re: Suggestions
(1) do not use R1 and R6: just connect the GND of the MAX485s directly to 0V
(2) change R2 and R3 with much higher values from 10K to 100K
(3) why microcontroller HB5 uses TX only while HB7 controls RE/TE of the MAX485 transceiver?
Regards
7447 multisim example vcc pin
Yes, sorry ... I meant "power" pins.
In real-world circuits, it's suggested to put a 0.1uF capacitor between VDD and VSS of a device every few device to filter high frequency noise generated by fast switching logic devices.
ripple-blanking input
The circuit seems basically correct.
Just some note:
* the clock frequency of 1kHz is very high for a display. You'll be unable to see the number changing. Try with much lower frequency like 1 or 2 Hz
* the BI/RBO pin is a strange input/output pin. Leave it unconnected...
ripple-blanking
Don't think so. Propagation time in standard TTL is very fast. Maybe some pin left open even if in TTL logic, an unconnect pin should be read as '1'.
Try posting the schematic.
ripple blanking
LT is a LAMP TEST input. It's active low so when at logic level 1, it has no effect; when at logic level 0, every output is active so you can check if a segment or an output is broken.
RBI is RIPPLE BLANKING INPUT is used in multi-digit display and should be connected to the...
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