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This page is no longer being updated. Please check out my new site dedicated to setting up LEDs with an aquarium using a TC420 at www.TC420.net.
www.TC420.net is constantly being updated and has cool calculators, more instruction, and will feature much more help and content.

Instructions for the TC420 Programmable LED Time Controller

I've started using the TC420 Programmable LED Time Controller to add a sunrise/sunset effect to my LED lit aquariums. As there was not a lot of information about the TC420 and I found a few issues with it so I created a video to show how I set up the controller on my bedroom aquariums. The video got a lot of views and a lot of questions, so I thought it would be useful to create a page to show how to set up the TC420 in detail and answer any questions that have been asked in the YouTube comments. So this is my instructions for the TC420 Programmable LED Time Controller.

This page is going to be pretty big, so I've set it up with its own menu to make it easier to navigate, you can find this at the top right of the page. Using this, you can jump to a specific part of the instructions,.If you find any of this information helpful, you could always thank me with a kind gift from Pro Shrimp.

Butterfly fish and the TC420 Controller

About The TC420

The TC420 is a simple, programmable time controller that can alter the brightness of up to 5 channels, each channel supporting a maximum of 4 amps. As an idea of what this can run, my Dad is using a single TC420 to control the main and sump lights on two marine aquariums, a 4' 400 litre system and a 2' 110 litre system.

The controller is programmed by a PC via a USB connection. The controller then performs the desired changes via it's 5 control ports. Input to the unit should be via a regulated power supply rated at 12v to 24v, but make sure the power supply is rated at the same voltage as your LEDs, or that you have a converter to make it safe. The TC420 uses Pulse Width Modulation (PWM) to alter the brightness of the LEDs. What this means is that the TC420 flashes the LEDs on and off extremely quickly, the slower the flash, the dimmer the LEDs appear.

The controller can be found on eBay for about £18. Use this search to see the product, and use this search to find it cheaper.

Connecting the Hardware

LEDs - Basic & Strip LEDs

This section describes using regular LED strips or modules, designed to be used with a 12v DC power source. If you are using high power LEDs such as luxeon star or the high power CoB LEDs, please see the LEDs - High Power LEDs section of this page.

The TC420 uses a common anode (+) system. This means that all the anodes (+) of the LEDs are joined together and the fades are controlled with the cathodes (-). In most cases, this won't have an effect on you, the exception being if you are planning to use RGB or RGBW LED strips. If you are using either of these strips, you must get common anode strips.

All other LEDs usually have a separate anode (+) and cathode (-), so you can pretty much get what you want. In some instances you could use the controller to control a circuit to operate lights which need more power or different value of power, but that's outside the scope of these instructions.

To connect the LEDs to the controller, simply connect the anodes (+ wire) of all the LEDs to the v+ terminal on the controller. Next, connect the cathodes (-) to the chX- terminal for the channel that you would like to control the LEDs that you are connection.

TC420 wiring diagram

Each channel can handle a maximum of 4 amps. To calculate the amps, you need to know how much power the LEDs use. Module LEDs will usually give you a wattage and voltage on the packaging, for example 1.44 watts and 12 volts DC. Strip LEDs will be 12v and the watts will usually be given to you per metre, for example a typical 5050 chip LED strip will be 14.4 watts per metre.

Modules example

Lets say you have 20 of the 1.44 watt LED modules. You multiply the 1.44 (watts) by 20 (quantity), then divide that by 12 (the volts) and that will give you the amps.

amps = (1.44 * 20) / 12
amps = 28.8 / 12
amps = 2.4

Strip example

Lets say you have 75cm of the 5050 chip LED strips. You multiply the 14.4 (watts) by 0.75 (length), then divide that by 12 (the volts) and that will give you the amps.

amps = (14,4 * 0.75) / 12
amps = 10.8 / 12
amps = 0.9

You will need these values to make sure the current flowing through the TC420 is not too great, and to specify the power of the transformer you need.

LEDs - High Power LEDs

This section will deal with connecting High Power LEDs to the TC420. I am looking to add 10 10w CoB LEDs to my 6' aquarium. I hope to have this worked out shortly. At the moment I'm still in the theoretical stage, and don't want to post anything here until I have a working system. For more information on my goals, please check out my 6' tropical aquarium page.

The Transformer / Driver / Power Supply Unit (PSU)

Firstly, I'd like to define what I'm talking about in this section, as this device seems to be called by many names on eBay and when people ask me questions. All the names are correct, though each implies a slight technical difference.

To be clear, if I talk about transformers or power supplys /PSUs, I am referring to the device you plug in the wall and it outputs 12 volts DC. If I talk about drivers, I'm meaning actual driver circuits used to provide a constant current.

Selecting the right transformer and setting it up

The transformer connects to the input v+ and v- terminals on the controller. It supplies power to both the TC420 and the LEDs, so you must get a transformer with enough power for these devices.

In the previous sections, I showed you how to calculate the amps for your LEDS. To calculate the size transformer you need, you must add the amps for all 5 channels together and add 10% as a safety margin. This will give you the smallest transformer size in amps. In the following example, I'll be using the following amp values for channels 1 to 4: 2, 1.5, 0.6, and 1.1.

amps = (2 + 1.5 + 0.6 + 1.1) x 1.1
amps = 5.2 x 1.1 (Multiplying by 1.1 adds 10% to the amps)
amps = 5.72

So we would need a 12v transformer rated at 5.72 watts or above. If the transformers are sized in watts, we must multiply the amps by the voltage.

watts = amps x volts
watts = 5.72 x 12
watts = 68.64

So we would need a transformer rated at 70 watts or above.

Questions - Drivers

Coming soon...

Questions - Lights off

I've been asked about power supplys, what happens to them when the lights are off, and if it's a good idea to have the power supply on a wall timer; the idea so that the power supply is off when the lights are off and rely on the TC420's battery backed up memory to keep time. First I'll start with is it possible, then I'll tackle is it worth it.

Is it possible?

I'm going to start with the battery backup, as if this can't keep time for the hours that the power is off, then this whole setup is doomed to failure. The average aquarium light is on for 6-10 hours a day, depending on what you are keeping. For testing the extremes of the battery, we'll go for a 6 hour set-up which would mean our PSU is off for 18 hours, so that will be the goal for my test. So far, I've had a TC420 disconnected from a power supply for 12 hours and it was fine. I will test out the full 18 hours when I get a new TC420 in a few weeks time.

I'm fairly confident that it will easily last the 18 hours. It most likely uses circuitry similar to that of an electronic wall timer, and I've had those things go without power for months and still be correct within an acceptable margin. My biggest concern would be the longevity of this, and if the battery would be happy with daily charging and discharging like that. However, for now I'm going to say yes, this is possible.

Is it worth it?

To me, this is the more interesting part of the question, and this time I'm pretty sure the answer is going to be no. Power supplys do not constantly produce the levels on the casing, that is their maximum level and will only supply what is being asked of it, plus about 10% which is lost in the efficiency of the transformer its self. When no current is being drawn, a power supply should only be ticking over at around 0.25 watts; the more efficient the power supply, the less it will be.

Test plan

I am going to measure the watts of an unconnected power supply, then connect only the TC420 to see how much that draws. This will give us an approximate figure for the TC420 in, what I'd call, standby mode, which is when it's connected but no LEDs are on. Once we have this figure, I'll measure some normal wall timers and see how many watts they use. In the case of a mechanical wall timer, it has to operate a motor to turn the time dial, and a digital timer is likely to have a circuit very similar to what is in the TC420.

The questions are:

I'll get these answers here soon, so stay tuned.

Programming the TC420 Controller


Before you can program the the controller, you need to install the software for the TC420; this is called PLed and is supplied on a mini CD with the TC420. Once installed, PLed will open and be ready to use.

NOTE: With some versions of the PLed software, I was unable to access all 5 channels. I have found a version which works fine with all channels, which you can download here. I recommend first installing the version that came with your TC420 and only installing this version if yours does not have support for all 5 channels.

About PLed

PLed is quite a simple program to use, once you get the hang of it. the interface is divided into three main sections, allowing you total control over your lighting with alternative configurations and different set-ups.


TC420 PLED packages menu

Packages are groups of modes. You will most likely have a single package for each TC420 that you have, so I find it useful to label the TC420 and give the package the same name as the label. There really isn't a lot to do with packages, as they're really just a container for the important bits, but here are the features you need to know about.

TC420 PLED packages menu - new

This button opens the New Package box. This is the first thing that you will need to do.

TC420 PLED new package dialog box

This is a pretty standard windows new file box, the only things you need to take note of is:
a) If you want to change the location that the files are saved (PackagePath), there is no new folder option in the change location dialogue box, so you will need to create the folders before hand.
b) By default, only 4 channels are selected, so change this to 5 (see highlight in the picture). Even change this if you don't think you'll be using all 5 channels to begin with.

TC420 PLED packages menu - open

This button lets you open your saved packages.

TC420 PLED packages menu - save

This button saves the current package you're working on.

TC420 PLED packages menu - download

This button uploads the open package to the TC420.

TC420 PLED packages menu - sync clock

This button synchronises the time on the TC420 with the time on your computer.

Mode List

TC420 PLED mode list menu

The mode list allows you to create different lighting schemes that are easily switched directly on the TC420. For example, you may have a normal setting which has the lights at full brightness, then an acclimation setting which has the main lights off, or at 25% brightness. You can have up to 50 modes. Again, there is not a lot to modes, they are just a useful tool for having multiple lighting modes on a single controller that are easily changeable.

TC420 PLED mode list menu -new

This button lets you create a new mode. Once created, double click on the mode's name to rename it.

TC420 PLED mode list menu - delete

This button deletes the currently selected mode.

TC420 PLED mode list menu - import

This button lets you import a previously exported mode into the current package.

TC420 PLED mode list menu - export

This button exports the selected mode so that you can import it into another package. You do not need to export the mode to save it.

TC420 PLED mode list menu - move

These buttons allow you to re-order the modes.

TC420 PLED mode list menu - edit

This button opens up the lighting edit dialogue in the selected mode. We will cover this in the next section.

Step Editor

TC420 PLED step edit box

The step editor is the tool for actually setting the light values for each channel. To open the step editor, select the mode that you want to edit, then click on the TC420 PLED mode list menu - edit edit mode button or double click in the steps pane. If you already have steps, you can double click on the step that you want to edit.

This is the "step editor" dialogue box, for editing the lighting values. If this is the first step in a new mode, most of the options will be greyed out until you click the Add button, to add the first step. Clicking the Add button more will add extra steps, but it's better to click it once you have set what you want in the current step. Once you have a step, you can edit the values.

After this, you can use the Add button to add another step to the mode or use the Prev and Next buttons to navigate through the steps you have already created. Keep adding or changing the steps until you have completed the mode, which could look something like this.

TC420 PLED completed mode

NOTE: I have discovered a bug with the controller that seems to effect modes that are transitioning over midnight, in that they don't fade smoothly over midnight. The best fix I have found to minimise the problem is to add steps at 23:59 and 0:00 and manually add the fade levels to these times using my tool below.

One change to rule them all

There is one problem with the PLed Step Editor, which is that every step effects all channels. What I mean by this is that if you want Channel 1 to be at 0% at 9:00 and 100% at 10:00, that's fine. But, as soon as you want to have Channel 2's brightness to be 0% at 9:30 and 100% at 10:30, things get more complicated. This is because all channels get effected at each step.

TC420 PLED steps time

It's a shame that there isn't a magic Fade option, where PLed will know that you want to continue fading between these times and calculates the level for you; that would be a very handy feature. What you have to do instead is calculate it yourself. You need to calculate what the light level will be at the intermediary point. In this example, it's pretty easy as we're starting at 0%, ending at 100%, and are fading over an hour. The intermediary points are exactly half way through the hour, so the lighting level is going to be 50%. See the highlighted values in the image.

To be honest, this is such a pain in the arse that I've written a tool to calculate these intermediary values. The tool can be found directly in the page contents for ease of access, or just see the section below.

Step Editor Intermediary Time Tool

To use this time tool, enter the start time, end time, and values for the channel with the gap in boxes for Channel A, then enter the intermediary time in the box for Channel B. Click the Calculate button and the value will appear.

Channel A Start Time point   Channel A Start Value
Channel B Time point   Channel A Mid Value
Channel A End Time point   Channel A End Value

To make it easier to understand, I have used the values from the following example.

TC420 PLED steps time

I am using CH1 as Channel A, with the intermediate being worked out as the highlighted value at 9:30.
If you have more than one gap that you need to calculate the values for, enter the start and end times and values in Channel A, then enter each intermediary time into Channel B and calculate them one at a time.

Uploading to the TC420

The final step is to upload your package to the TC420. This is a simple step-by-step procedure:

  1. The first thing to do is save your package by clicking the TC420 PLED package menu - save button.
  2. Connect the TC420 to your computer with a USB cable.
  3. If the TC420 is not recognised, disconnect the USB cable, switch off the power transformer connected to the TC420 controller and try plugging in the USB cable again. If your TC420 can be connected to the transformer and USB at the same time, you will be able to use the demo functions, if not you won't.
  4. Once the TC420 is recognised by the computer, click the TC420 PLED package menu - sync clock button to synchronise the time.
  5. Click the TC420 PLED package menu - download button to upload your package to the TC420.
  6. Disconnect the USB from the TC420.
  7. If you switched off the power transformer, switch it on and your lighting scheme will run.

Your lighting package should now be running on your TC420. To change the mode, you can enter the menu and use the buttons to increment through them. The modes will be in the same order as they are in the package in the PLed software. I hope this guide gives you a good head start for using the TC420. It will be growing as I learn more, and I will be adding features to make using the device even quicker and easier for you. If you find any of this information and the tools helpful, please feel free to show your thanks with a kind gift from Pro Shrimp. Good luck with your projects.