Direct Digital Synthesizer Kit
Alternate LCD USE

There is a 10 pin header (2x5, 0.1 in spacing) near the top of the board.  Full kits are shipped with my Serial LCD module.  To use this LCD simply wire straight through (Pin 1 to pin1 of the LCd etc.) J4 jumper must be installed. The Microprocessor tests this line at power up and will use the appropriate LCD routines depending on the presence or absence of this jumper.  If you remove the jumper, and connect a industry standard 14 pin HD44780 LCD module it will also work nicely.  Most any LCD with  at least 8 digits and a Hitachi HD44780 or equivalent (KS0066, S6A0069) LCD controller.  An 8x2, 16x2 or 16x1 format will work, a 8x1 format will work but only the frequency will be displayed, there's no room for memory number etc.  You can also use larger displays, i.e. 20x4 or 40x4, but the extra space is not used.  My DDS board uses a 4 bit interface to the LCD, which is a standard option with the HD44870 chip, there are a few LCD modules out there that only have 4 bits brought out which is fine they should work.  Some LCD modules, such as the Data Vision 16110 work but require a negative Vlcd voltage (1~2v) which you will have to supply.

 In the photo you can see an assortment on LCD modules that I have been working with.  The large one at the bottom of the photo is used on my frequency counter and will be shipped with the kit.  It's very inexpensive, has very large high contrast digits. The others were obtained from a variety of sources, I paid between $2 and $10 for them. Some have backlights.  Some might fit inside the Altoids tin with the PCB.  At this point it is unlikely I will be stocking  or selling any of these other displays.   Scroll down for some links to suppliers. 

LCd options
Expect for the tiny one on the top all of these have been tested and work.  The tiny one on top is from electronics goldmine and looks promising, but has a tiny flat cable connected to it and I haven't yet have the patience to wire it up.

Note pin connection info in this table does not apply to Oct 2011 PCBs and later
They have on board connectors for various LCD types
HD44870 Pin #
Signal Name
Connect to PCB

Connecting your backlight.  If your display has a LED backlight, it is usually (but not always) connected to pins 15 and 16. Normally the anode of the LED connected to pin 15, and the cathode to pin 16.  In general you should connect the cathode (pin 16 ) to ground, and supply power through a dropping resistor to the anode.  In some cases there is a dropping resistor on LCD module.  But it's safest to start with a dropping resistor of 180 ohms or so, then adjust the value for the brightness you want. You could install a pot if you want adjustable brightness.  If you need to put more than about 50mA through the backlight LED (unlikely) I would suggest you use a separate voltage source because the 5v regulator on the DDS may overheat.  I you happen to have an LCD module with a CFL backlight, good luck with that, they need a high voltage power source.

VLCD Most LCD's have a separate voltage usually called VLCD, pin3 on the standard pinout.  However, the voltage is not standard.  Some LCD's simply require 0v (ground) on this line.  Some require a negative voltage in the range of -0.5 to -1.5 volts.  But most work with something in the 0 to +2.5v range, which the 1K resistor &1K pot combination generate.  My serial LCD can use the 0-2.5 adjustable voltage, or simply a 10K resistor to ground works fine.

Manufacturer Part # Format Type Backlight Backlight Resistor Overall Dim Cost Min S/H Vlcd Comp. w/ N3ZI DDS
Advantages Disadvantages Source
ModuleHouse KTM-S1201 12x1 Numeric None N/A 4.9 x 1.3 x 0.4 FREE FREE Fixed 10K to Gnd Compatible Large highly visible digits, low cost too big for small radios, no text N3ZI
Orient AMC1601AR 16x1 Alpha LED 47 ohm 3.2 x 1.4 x 0.6 $4 $7 Ground Compatible Nice, Readable, nice backlight large Characters Slightly Noticeable Reflection ShopEIO
Electrolyte QY-162A 16x2 Alpha LED 47 ohm 3.2 x 1.5 x 0.6 $4 $4 1K + 1kTrim Pot Compatible Very Readable, Avail in different colors Thick, Backlight not as uniform as others Ebay/ FCB Electronics
JHD JHD802A 8x2 Alpha LED 47 ohm 1.7 x 1.4 x 0.3 $5 FREE 1K + 1kTrim Pot Compatible
Mediocre contrast, only 8 char's per line Ebay/ szdigitalsquare
SURE DE-LM001 8x2 Alpha LED 47 ohm 1.7 x 1.4 x 0.6 $6.50 FREE Ground Compatible Nice,  Readable, nice backlight Thick, only 8 char's per line Ebay/ SureElectronics
Truely MCC162C4 12x2 Alpha None
3.3 x 1.4 x 0.3 $4 $7 1K + 1kTrim Pot Compatible
Mediocre contrast ShopEIO
Sharp LM16255 16x2 Alpha None N/A 3.2 x 1.9 x 0.4 $2-$5 $7 1K + 1kTrim Pot Compatible
Mediocre contrast ShopEIO, All Electronics
Seiko C550001 16x2 Alpha LED 22 ohm 2.7 x 1.0 x 0.5 $3 $7 -0.4 to -1.4 volts Compatible, but needs negative voltage for LCD Nice Compact Display Negative Voltage needed, Thick, only fair contrast ShopEIO
Datavision 16110 16x1 Alpha None N/A 4.9 x 1.4 x 0.4 $2-$5 $7 -0.4 to -1.4 volts Compatible BUT Requires Negative Voltage for LCD Very Readable without backlight Requires Negative Voltage for LCD Electronic Goldmine, ShopEIO
Shin Nichi LCM-5016-67HR 16x2 Alpha EL N/A 3.1 x 1.4 x 0.4 $3 $7 ? Should work, but it doesn't. No data
My sample didn't work at all ShopEIO
Hantronix HDM16216L 16x2 Alpha LED N/A 2.2 x 0.8 x 0.4 $4 $7 ? I'm working on it, should work, but very difficult I/O cable connector Electronic Goldmine
Wintek WD-C2401P 12x1 Alpha None N/A 4.2 x 0.7 x 0.4 $2 $7 None Nope, oddball interface
Won't work All electronics, Electronic Goldmine

BACKLIGHTING:  My personal opinion is that back lighting is overrated.  LCD's can be reflective, transmissive, or transreflective.  Reflective means they reflect 100% of the light coming in.  Transmissive means they pass 100% of the light from behind.  Transreflective LCDs are a compromise, they reflect 50% and transmit 50%.  With transreflective LCD's frequently a shadow is very noticeable, one image from the backlight and one from the room light.  Most of the  LCDs above are transreflective.  The ones with backlights are very readable when the backlight is on, barely readable when it's off.  The ones without backlights have only fair contrast. The serial  LCD is 100% reflective display and has excellent contrast  Very readable in low room light, but not readable in the dark.

Also the LED backlights require a decent about of current.  You almost always need to install a separate resistor in series with the backlight LED to limit current.  In most cases 47ohms is a good choice.  But this will approximately double the current draw of the DDS VFO.  Please do not draw more than 50mA through the DDS PCB unless you heatsink the 7805 regulator.  If you are operating portable, consider an LCD without a backlight, or put a switch in line to turn off the backlight when you don't need it.

If you happen to have an LCD modules or find one on-line that looks nice, email me the info about it and I'll see if I think it will work.  If you want, you can send it to me, with a few $ for return postage, and I'll test it and return it.  A LCD module with controller is needed, simple LCD glass does not work.

All Electronics (LCD-111 Wintek C2401P will not work)
Electronics Goldmine (Low prices, small quantities, selection varies)
SHOPEIO (Great selection, some expensive, some bargains) No Longer Recomended
Ebay (search for LCD Module)