# VMC and PCC Power

Two main components of your Phase II build are the **Vehicle Management Computer** (VMC), which runs the VRC software stack and the **Peripheral Control Computer** (PCC), which will allow teams to manually and programmatically control the LED ring and actuate up to four servos.&#x20;

This section will walk through the necessary steps for providing adequate power to both the VMC and PCC. This will be done with two separate buck converters, which are included in **Box 5** of your kit. The main battery of your VRC drone is 16.8V fully charged. The required input voltage for the VMC and PCC are 5V, therefore the buck converters will step the voltage down to a usable 5V.

## VMC Buck Converter

The following steps will be repeated for both buck converters and connected to the PDB of the VRC drone. Start off by locating the heat shrink tubing and male bullet connectors as seen below.

![Heat shrink tubing, bullet connectors, and buck converter](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjVGs3vRzxKvreebBkh%2F-MjVQ_awBEWXQQLDYQ29%2Fbullet_connectors1.jpg?alt=media\&token=f43b6426-cb1a-440c-b718-9b465262e826)

{% hint style="info" %}
The heat shrink tubing will be longer than necessary. Cut two pieces of tubing approximately 2" in length using scissors.
{% endhint %}

Place heat shrink tubing over the black and red leads of the buck converter. Clamp one of the bullet connectors using the tool of your choice and fill the cup with solder.

{% hint style="info" %}
If you don't have a tool to hold the bullet connector one thing you can do is drill a hole into a small piece of wood, such as an old piece of 2x4, and place the bullet connector into the hole with the cup facing up.
{% endhint %}

![Filling the bullet connector with solder](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjVGs3vRzxKvreebBkh%2F-MjVQsc5rKM_yDo0T4JA%2Fbullet_connectors2.jpg?alt=media\&token=e101e3dd-8029-4b99-9ea1-a547c1cdd39b)

Quickly remove the solder tip and place one of the black or red leads into the cup. Keep it there for a few seconds until the solder hardens.&#x20;

{% hint style="danger" %}
Bullet connectors conduct a lot of heat, so make sure not to touch the connector for a minute or two after it's filled with solder.
{% endhint %}

![Positive and negative leads with bullet connectors soldered](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjVGs3vRzxKvreebBkh%2F-MjVSneobGuRkH6-X4NU%2Fbullet_connector3.jpg?alt=media\&token=ba7dcb64-fa3e-44f3-95bc-db0373832469)

After the bullet connectors are soldered into place you will apply the heat shrink. Pull the heat shrink down over the end of the bullet connector as shown in the photo below and apply heat. If you have access to a heat gun or a lighter this will work well. Alternatively, you can use the side of your soldering iron to apply heat and let the tubing shrink over your connectors.

![Apply heat shrink with asoldering iron](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjdrPrhgWnh2Cd_g1UJ%2F-MjetGuinI3ezn1Y7Y7r%2Fheat_shrink_soldering_iron.jpg?alt=media\&token=6788fced-4847-4547-9b13-a58b6f348228)

After applying heat shrink to the bullet connectors they should look similar to the photo below.

![Bullet connectors and heat shrink applied to VMC buck converter](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjetIIp4cTQiTzq0aa6%2F-MjeyGJkTk7JJd9FztlO%2Fheat_shrink_complete.jpg?alt=media\&token=a7b40b27-a5a8-414d-a853-3b694d9b7385)

With the input side (16.8V) of the buck converter complete we need to take care of the output side. This is what we will plug into the VMC using a DC barrel plug to provide a constant 5V. The barrel plugs are located in **Box 5** of your VRC kit.

![Barrel plugs from the VRC kit](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-Mjez8-8EY0BtRGYrw4M%2F-Mjf3HSfukWzF6cdWYRq%2Fvmc_barrel_plug.jpg?alt=media\&token=213a7dab-bf11-4494-ac15-6c2beff4f54b)

Out of the package the barrel plugs are longer than necessary. Cut one to approximately 4-5" which is a good length that we'll solder to the black and yellow leads of the buck converter.

![Barrel plug trimmed and ready for soldering to buck converter](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-Mjf4YhD5Ln0S6pN_BmH%2F-Mjf7u_niv2Q9QmE-EGi%2Fcut_barrel_plug.jpg?alt=media\&token=872c1413-580c-4cb0-9430-f42a30d423bc)

We will prep the black and yellow leads with heat shrink before soldering begins. The photo below shows heat shrink over each of the individual leads and a larger piece covering both leads. This will allow us to keep our connections nice and tidy.

{% hint style="info" %}
Be sure to slide the heat shrink onto the leads **BEFORE** soldering. Otherwise you will not be able to do so after soldering is complete.
{% endhint %}

![Black and yellow output leads prepped with heat shrink and ready for soldering](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-Mjf4YhD5Ln0S6pN_BmH%2F-MjfKgivtp4cXP5vfpl1%2Fbuck_converter_heat_shrink_for_barrel_plug.jpg?alt=media\&token=88f44987-b992-4c98-ace8-4e036f4de5f6)

Soldering two leads together isn't always the easiest chore so be sure to use the right tool to keep the leads steady and then solder them together.

{% hint style="warning" %}
It's incredibly important that you solder the **RED** lead from the barrel plug to the **YELLOW** lead of the buck converter. Then the **BLACK** lead from the barrel plug to the **BLACK** lead of the buck converter.
{% endhint %}

![Red and yellow wires soldered together](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjfaPt1TttAwK9THFKy%2F-MjfbSjpPDDqIeW1QFaN%2Fsolder_buck_converter_output_leads.jpg?alt=media\&token=fd80f32a-4f51-4ece-8d2f-6de562d9ca19)

After soldering the leads together you should have something that looks like the photo below.

![Positive (red/yellow) and negative (black/black) wires soldered together](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjfbcgE4SWBT6PvF0ZY%2F-MjfcCwgI6a5Gz26qB3Z%2Fbuck_converter_output_leads_soldered.jpg?alt=media\&token=be5acc25-3e39-453a-938e-8503579a21dd)

Given we want to prevent a short circuit between the positive and negative connections we will apply heat shrink to the solder joints.

![Positive and negative joints with heat shrink applied](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjiokWz_DG47Qk4MqnX%2F-Mjiy2qVupg8N9p-d7gM%2Fred_yellow_barrel_plug_and_buck_converter.jpg?alt=media\&token=8e4e4523-8987-4d1e-b061-075b8781032f)

Slide the last piece of heat shrink down and apply heat to it. This step is completely optional, but it does help keep your cable nice and tidy.&#x20;

![Barrel plug connected to buck converter and ready to power VMC](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjiokWz_DG47Qk4MqnX%2F-Mjj2T9OB-eQPq2QK5Fs%2Fbuck_converter_complete.jpg?alt=media\&token=6d5815d0-33a7-46cd-a75c-965caaf13a53)

Good job! Now let's quickly go over how to get the other buck converter ready for the PCC.

## PCC Buck Converter

The PCC requires 5V of input power and will use the second buck converter in your VRC kit. Follow the steps covered in the VMC power setup by soldering bullet connectors to the red and black leads of the buck converter.

![Bullet connectors and heat shrink applied to PCC buck converter](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjetIIp4cTQiTzq0aa6%2F-MjeyGJkTk7JJd9FztlO%2Fheat_shrink_complete.jpg?alt=media\&token=a7b40b27-a5a8-414d-a853-3b694d9b7385)

For now we won't do anything with the PCC power leads (yellow/black) and will connect them to the PCC in a future step.

## Connecting Buck Converters to PDB

With the VMC and PCC buck converters ready to go we will now connect them to the PDB of the VRC drone. If you recall from Phase 1, the PDB sits in between the top and bottom plates of the frame. **Remove the top plate of the frame to expose the PDB**.

After removing the top plate make sure to plug the VMC buck converter into the female bullet connectors on the right side of the PDB. This will put the barrel plug on the same side of the VMC input jack, after we mount it in a future step.

{% hint style="info" %}
If you're wondering which side is the "right side", we are referring to the right side with the nose of the VRC drone pointed away from us and looking down on the frame.
{% endhint %}

{% hint style="warning" %}
Be sure to plug the red lead from the buck converter into the positive terminal on the PDB. It will also be red as shown in the photo below. Then proceed with black to black.
{% endhint %}

![VMC buck converter plugged into PDB](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjjP3MI6LTZ0HvjvPfF%2F-MjjQI_AnnTROaLf6aDH%2Fconnect_vmc_buck_converter.jpg?alt=media\&token=73e77ae4-46ef-4266-8ca0-2863a90c562e)

Repeat the process for the left side of the PDB, which will provide power to the PCC buck converter.

![PCC buck converter plugged into PDB](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-MjjTxH38cFDSiJDN58_%2F-MjjX5bUp6UprShsgII4%2Fpcc_buck_converter_pdb.jpg?alt=media\&token=e7ac8a78-d90a-49d6-84ea-be2330a94341)

{% hint style="danger" %}
Please do not power your VRC drone until the PCC power leads (yellow/black) have been connected. Otherwise you will run the risk of the leads creating a short circuit since they are exposed. To be extra safe you can apply heat shrink or electrical tape to the exposed wires.
{% endhint %}

## Remove Landing Gear

The buck converters will be mounted where the existing landing gear are attached. It's much easier to remove the landing gear with the top plate removed, so let's go ahead and do that. In the next section we will upgrade the landing gear, which will provide plenty of clearance beneath the VRC drone. This will be very important for the Phase II competition.

![Phase 1 landing gear ready to be removed](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-Mjjd3kEuoNu4DycleBZ%2F-MjjtI-Dbjl8E9QnJwlQ%2Flanding_gear_attachment.jpg?alt=media\&token=1a5a7c91-76dd-4677-b501-d9a84b7e4517)

## Mounting Buck Converters

The final step is to attach the buck converters to the bottom plate of the VRC drone frame. We recommend using a strong double-sided adhesive such as the 3M tape available at your local hardware store.

![Buck converters attached to bottom plate](https://2067701961-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MiT5g4L04alXNmboKaR%2F-Mjj_QMSQpnlFcr8_qEU%2F-MjjaHI908M2kRNoDEXS%2Fbuck_converters_attached.jpg?alt=media\&token=14ee7797-3769-4b78-94dc-358c79792954)

{% hint style="info" %}
Don't attach your top plate just yet! We need to keep it removed for the next section.
{% endhint %}

